CRaTER: Lunar Proton Albedo Anomalies

Figure 1. Top: Lunar albedo proton yield map (cylindrical projection) with anomalous yield regions labeled “A” through “E”. Regions A (Mare Serenitatis) and B (Oceanus Procellarum) are both centered near the boundaries of mare regions. Regions C, D and E are all in the highlands on the far side of the Moon. Bottom: Visible global composite image from the Lunar Reconnaissance Orbiter Camera (LROC).

LUNAR PROTON ALBEDO ANOMALIES:
SOIL, SURVEYORS, AND STATISTICS

J.K. Wilson, N. Schwadron and H. E. Spence, et al.
Space Science Center
University of New Hampshire, Durham

Introduction: Since the launch of the Lunar Reconnaissance Orbiter (LRO) in 2009, the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) has been mapping albedo protons (~100 MeV) coming from the Moon [1,2].

These protons are produced by nuclear spallation, a consequence of galactic cosmic ray (GCR) bombardment of the lunar regolith. Just as spalled neutrons and gamma rays reveal elemental abundances in the lunar regolith [3-6], albedo protons may be a complimentary method for mapping compositional variations across the Moon’s surface.

Albedo Proton Yield: The CRaTER instrument simultaneously detects albedo protons from the Moon and GCRs arriving from the zenith direction. We divide the number of albedo protons observed over each point on the Moon by the number of GCRs detected over the same location to produce a map of the yield of albedo protons.

We presently find that the lunar maria have an average proton yield which is 0.9% ± 0.3% higher than the average yield in the highlands; this is consistent with some neutron data that shows a similar yield dichotomy due to differences in the average atomic weight between mare regolith and highland regolith [7].

Map Features: There are cases where two or more adjacent pixels (15° × 15°) in the map have significantly anomalous yields above or below the mean.

These include two high-yielding regions in the maria, and three low-yielding regions in the far-side highlands. Some of the regions could be artifacts of Poisson noise, but for completeness we consider possible effects from compositional anomalies in the lunar regolith, including pyroclastic flows, antipodes of fresh craters, and so-called "red spots" which are associated with volcanic domes. We also consider man-made landers and crash sites that may have brought elements not normally found in the lunar regolith.

References: [1] Wilson, J. K. et al. (2012) JGR, 117, E00H23. [2] Spence, H. E. et al. (2012) Space Weather, 11, 643-650. [3] Feldman W. C. et al. (1998) Science, 281, 1496-1500. [4] Gasnault, O. et al. (2001) GRL, 28, 3797-3800. [5] Maurice, S. et al. (2004) JGR, 109, E07S04. [6] Mitrofanov, I. G. et al. (2010) Science, 330, 483-486. [7] Litvak, M. L. et al. (2012) JGR, 117, E00H22.

Live CRaTER data from LRO re-broadcast as music

CRaTER, now half way through its fifth year in lunar orbit onboard LRO, is providing a solid data set on the real health hazards and possible mitigation of high-energy radiation from deep space in Earth's vicinity and in low lunar orbit, where the Moon effectively shields half the sky. Using proven technologies cosmic - not solar - radiation is a significant block to long-term human spaceflight beyond the Moon [NASA/GSFC/UNH/SwRI].

Elizabeth Zubritsky
Goddard Space Flight Center

The latest tool for checking space weather is an internet radio station fed by data received from NASA's Lunar Reconnaissance Orbiter (LRO).

The radio station essentially operates in real time, receiving measurements of how much radiation the spacecraft is experiencing and converting into a constant stream of music. The radiation levels determine which instrument is featured, the musical key being used and pitches played.

"Our minds love music, so this offers a pleasurable way to interface with the data," said the leader of the music project, Marty Quinn of the University of New Hampshire, Durham. "It also provides accessibility for people with visual impairments."

The radiation levels are determined by LRO's Cosmic Ray Telescope for the Effects of Radiation (CRaTER). Equipped with six detectors, CRaTER monitors the energetic charged particles from galactic cosmic rays and solar events.

The instrument makes two kinds of crucial measurements. One type studies the interaction of radiation in space with a material that is like human tissue; this is helping scientists assess the effects that exposure would have on people and organisms. The other type looks at radiation hitting the moon and the products generated by that interaction, which provides a way to explore the composition of the regolith on the moon.

"CRaTER has discovered wide-ranging and fundamental aspects of such radiation," said Nathan Schwadron, the principal investigator for CRaTER. "For example, we have discovered that tissue-equivalent plastics and other lightweight materials can provide even more effective protection than standard shielding, such as aluminum."

Each detector on CRaTER reports the number of particles registered every second. These counts are relayed to CRaTER Live Radio, where software converts the numbers into pitches in a four-octave scale. Six pitches are played every second, one for each detector. Higher, tinkly pitches indicate less activity, whereas lower, somber-sounding pitches indicate more activity.

The software selects the primary instrument and a musical key based on recent activity. At the lowest radiation levels, the main instrument will be a piano, playing pitches from one of the major scales. But as the peak radiation level climbs, one of the minor scales will be selected instead, and the piano will be replaced by one of seven other instruments.

For example, when CRaTER picked up elevated radiation counts caused by the solar flare January 7, 2014, the primary instrument changed to a marimba, which is two instruments up from the piano. A steel drum or guitar instead of a marimba would mean the radiation level had ramped up more. A banjo would mean the peak had climbed to the top of the normal operating range.

If the counts climb beyond the top of the normal operating range – as might happen during a very big event – the software would switch into a second operating range. The piano would again represent the bottom of this range, and the banjo would represent the top. To indicate which range is current, a violin and a cello play sustained notes in the background. If those sustained notes are played at the highest pitches on the scale, the normal operating range is in effect; if those notes drop by even one pitch, the second range is being used.

The radio station is one of CRaTER's official data products and is available online and through an app. The data feed from LRO is live, with one caveat. Whenever the spacecraft moves behind the moon, it cannot line up with data-collecting antennas on Earth, so there is a blackout period of about an hour. During that time, the station reuses the previous hour's data. To indicate that the music is not live, the sound of the bongo drum in the background is changed, and the chiming of the triangle is muted.

The most familiar example of data sonification – conversion into sound – is a simple one: The Geiger counter produces a click every time it detects a radioactive particle.

In the past few decades, scientists in many fields have experimented with sonification, hoping to capitalize on humans' ability to hear small changes instantly, even against a noisy background. Music has the added advantage of making it easy to process many changes at once through variations in pitch, rhythm, tempo, scale, loudness and instrumentation.

"Music makes it easy for people to take in the data, and it seems to be a natural fit for space missions," said LRO's project scientist, John Keller of NASA's Goddard Space Flight Center, Greenbelt, Maryland.

Sonification has been used to present data from several NASA spacecraft, especially Voyagers 1 and 2 and the Kepler observatory. Quinn previously worked on sonification for other NASA missions, including Mars Odyssey, the Solar TErrestrial RElations Observatory, the Advanced Composition Explorer and the Interstellar Boundary Explorer.

More from CRaTER on radiation health hazards

CRaTER, in a fifth year in lunar orbit aboard LRO is providing a solid data set on the real health hazards, and possible mitigation, of high-energy radiation in deep space. Using proven technologies cosmic, not solar, radiation, is a significant block to long-term human spaceflight beyond the Moon [NASA/GSFC/UNH/SwRI].

David Sims
University of New Hampshire
Institute for the Sutdy of Earth, Oceans and Space

Scientists from the University of New Hampshire and colleagues have published comprehensive findings on space-based radiation as measured by a UNH-led detector aboard NASA's Lunar Reconnaissance Orbiter (LRO). The data provide critical information on the radiation hazards that will be faced by astronauts on extended missions to deep space such as those to Mars.

The papers in a special issue of the journal Space Weather document and quantify measurements made since 2009 by the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) radiation detector.

"These data are a fundamental reference for the radiation hazards in near Earth 'geospace' out to Mars and other regions of our sun's vast heliosphere," says CRaTER principal investigator Nathan Schwadron of the UNH Institute for the Study of Earth, Oceans, and Space (EOS).

The space environment poses significant risks to both humans and satellites due to harmful radiation from galactic cosmic rays and solar energetic particles that can easily penetrate typical shielding and damage electronics. When this radiation impacts biological cells, it can cause an increased risk of cancer.

Standard spacecraft shielding, integrated into hull design,
is strong protection from most solar radiation, but defeats
this purpose with high-energy cosmic rays it simply
splits into deadly showers of secondary particles [NAS].

Before CRaTER's long-term radiation measurements were derived using a material called "tissue-equivalent plastic" - a stand-in for human muscle capable of gauging radiation dosage - those hazards were not sufficiently well characterized to determine if long missions outside low-Earth orbit can be accomplished with acceptable risk.

CRaTER's seminal measurements now provide quantified, radiation hazard data from lunar orbit and can be used to calculate radiation dosage from deep space down to airline altitudes.

The data will be crucial in developing techniques for shielding against space-based radiation dosage. The measurements have also played a vital role in UNH space scientists' efforts to develop both the first Web-based tool for predicting and forecasting the radiation environment in near-Earth, lunar, and Martian space environments and a space radiation detector that possesses unprecedented performance capabilities.

The near real-time prediction/forecasting tool known as PREDICCS integrates for the first time numerical models of space radiation and a host of real-time measurements being made by satellites currently in space. It provides updates of the radiation environment on an hourly basis and archives the data weekly, monthly, and yearly - an historical record that provides a clear picture of when a safe radiation dose limit is reached for skin or blood-forming organs, for example.

CRaTER offers an opportunity to test the capability of PREDICCS to accurately describe the lunar radiation environment. The Space Weather special issue provides comparisons between dose rates produced by PREDICCS with those measured by CRaTER during three major solar energetic particle events that occurred in 2012.

The detector developed at UNH, known as DoSEN, short for Dose Spectra from Energetic Particles and Neutrons, measures and calculates the absorbed dose in matter and tissue resulting from the exposure to indirect and direct ionizing radiation, which can change cells at the atomic level and lead to irreparable damage. Schwadron is lead scientist for both the PREDICCS and the DoSEN project.

"DoSEN is an innovative concept that will lead to a new generation of radiation detectors, or dosimeters, to aid in understanding the hazards posed by the radiation environment of space," says Schwadron. "The ability to accurately understand these hazards will be critical to protect astronauts sent beyond low-Earth orbit on extended space missions."

DoSEN combines two advanced, complementary radiation detection concepts that present fundamental advantages over traditional dosimetry. The dosimeter measures both the energy and the charge distribution of energetic particles that affect human and robotic health in a way not presently possible with current technology. Protons, heavy ions, and neutrons all contribute significantly to the radiation hazard.

"Understanding how different particles such as neutrons and heavy ions pose hazards will be extremely important in completely characterizing the types of environments we will operate in," Schwadron says. "For example, on the Moon, there are additional hazards from neutrons that are created by high-energy radiation interacting in the lunar soil and radiating outward from the surface."

That 'backsplash" of protons, which was discovered by CRaTER and is known as the Moon's radiation "albedo," is caused by the partial reflection of galactic cosmic rays off the moon's surface. This creates a surprising one-two punch of deadly radiation and can also be used to peer below the lunar surface like a geological probe.

Says Harlan Spence, CRaTER deputy lead scientist and director of EOS, "Until now, people have not had the 'eyes' necessary to see this particular population of particles. With CRaTER, we just happen to have the right focus to make these discoveries."

UNH team members on the CRaTER instrument and co-authors on the Space Weather papers include Schwadron, Spence, Sonya Smith, Mike Golightly, Jody Wilson and Colin Joyce, Jason Legere, and Cary Zeitlin of the Southwest Research Institute Earth, Oceans, and Space Department at UNH. Coauthors from the UNH Space Science Center on the DoSEN project include James Ryan, Peter Bloser, and Chris Bancroft.

Figure 1. Wilson, et al, "First Albedo Proton Map of the Moon," Diagram of CRaTER instrument showing cross-sectional cutaway view of the stack of six detectors (D1–D6) and pieces of tissue equivalent plastic (TEP). Example particle trajectories are shown for a high-energy galactic cosmic ray from the zenith passing completely through the instrument (red line) and for an albedo proton (blue line) coming up from the lunar surface and passing through four detectors before being stopped in one of the blocks of TEP. (Adapted from Spence et al. [2010].)

Additional Background from NASA Goddard Space Flight Center:

Paul Gabrielsen
 
Radiation in deep space comes from cosmic rays, from the solar wind and from solar energetic particles emanated during a solar storm. Particles from these sources rocket through space. Many can pass right through matter, such as our bodies. So-called ionizing radiation knocks electrons off of atoms within our bodies, creating highly reactive ions. Within Earth's protective atmosphere and magnetic field, we receive low doses of background radiation every day. The radiation hazards astronauts face are serious, yet manageable thanks to research endeavors such as the CRaTER instrument.

CRaTER measures realistic human radiation doses at the moon using a unique material called tissue-equivalent plastic (TEP). Two pieces of this plastic, roughly 2 inches and 1 inch thick, respectively, are separated by silicon radiation detectors. The TEP-detector combo measures how much radiation may actually reach human organs, which may be less than the amount that reaches the spacecraft.

"Tissue-equivalent plastic gives us an idea of the self-shielding of the body," said Larry Townsend, of the University of Tennessee, Knoxville. "The radiation spectrum at the organs is not going to be the same as the radiation spectrum that's outside the spacecraft."

Townsend notes that CRaTER's observations have come at a time when solar activity, and hence the solar wind, has been unusually quiet. The solar wind disperses some galactic cosmic rays, but in the current solar lull, more of these rays are able to bombard the Earth and moon. CRaTER, which launched aboard LRO with six other instruments in 2009, has been able to monitor the lunar environment as solar activity has declined. Further mission extensions would allow additional detailed measurements as solar activity waxes and wanes.

"They're lower-level exposures," Townsend said, of galactic cosmic rays, "but they're damaging in the sense that the particles are highly charged and heavy, and they create a lot of damage when they're going through the body."

But lab tests suggested that materials rich in hydrogen, such as some plastics, may shield against these heavy particles, said Cary Zeitlin of the Southwest Research Institute, San Antonio, Texas. "The tissue-equivalent plastic in CRaTER has fairly high hydrogen content," he said, "so it lets us test this hypothesis using data from deep space. And it turns out that plastic really is a good shield against these particles, significantly better than aluminum."

LRO's unofficial motto states that "exploration enables science, and science enables exploration." The LRO spacecraft launched as an exploration mission, a forerunner for humanity's return to the moon. But after completing its primary mission in 2010, LRO has become a powerful instrument for lunar and planetary science. CRaTER is an active participant in this scientific study, discovering a previously unmeasured source of hazardous radiation emanating from the moon itself.

This radiation comes from the partial reflection, also called an albedo, of galactic cosmic rays off the moon's surface. Galactic cosmic ray protons penetrate as much as a meter (about 3.2 feet) into the lunar surface, bombarding the material within and creating a spray of secondary radiation and a mix of high-energy particles that flies back out into space. This galactic cosmic ray albedo, which may interact differently with various chemical structures, could provide another method to remotely map the minerals present at the moon's surface.

CRaTER directly measured the proton component of the moon's radiation albedo for the first time, said Harlan Spence, deputy principal investigator at the University of New Hampshire. The TEP radiation detector measures various components of radiation separately, which enables CRaTER to, in Spence's words, "unfold" the energy spectrum of the radiation albedo. This result, he said, illustrates the value of combining exploration and science in spaceflight. "If we had been on a different science-oriented mission, we probably would've developed a different instrument," Spence said. "In fact, we probably never would have flown TEP."

Looking toward future missions, Schwadron and his colleagues are developing a next-generation radiation dose detector, drawing on CRaTER's design. The detector, called Dose Spectra from Energetic particles and Neutrons (DoSEN) builds on CRaTER's ability to break radiation down into its components and assess the doses resulting from each part of the radiation spectrum. Human exploration will benefit, Schwadron said, from this "very specific information about the spectrum of radiation we need to shield against."

Spence, who served as the instrument's principal investigator through the primary mission said he's proud of his team's foresight to equip CRaTER with the capability to accomplish its mission and continue to pursue great science.

"We had hopes and aspirations," he said, "but we didn't think we would be able to reap as much from those data as we are. Exploration now is enabling science."

Related Posts:

CRaTER shows lighted materials may mitigate cosmic ray risks (June 12, 2013)

Cosmic Ray threat to manned spaceflight tested on MSL (May 31, 2013)
The radiation environment and its effects on human spaceflight: A Lunar Mission (January 5, 2013)
Cosmic ray flux effects lunar ice (March 19, 2012)
"A Perfect Storm of Cosmic Rays" (September 29, 2009)
Cosmic rays and manned space travel (September 16, 2009)
Cosmic ray flux highest ever recorded (September 3, 2009)
Returning to the Moon (August 9, 2009)
Skeptical: LUNAR-TEX radiation blanket (May 11, 2009)
NASA cataract detection down to Earth (January 18, 2009)
NASA and Congress sacrifice radiation shielding flexibility
removing dry landing hardware (May 17, 2008)

Managing Space Radiation Risk in the New Era of Space Exploration (2008)
Committee on the Evaluation of Radiation Shielding for Space Exploration
National Research Council

CRaTER on LRO shows lighter materials may better mitigate cosmic ray health risks

As CRaTER, flying with LRO, closes out a fourth year in lunar orbit, long duration exposure to cosmic rays while traveling within and beyond Earth's magnetic field shows materials lighter than traditional aluminum and titanium alloyed hulls may reduce the probability of Radiation Exposure Induced Death (REID) [NASA/GSFC/UHN/SwRI].

University of New Hampshire - Durham –- Space scientists from the University of New Hampshire (UNH) and the Southwest Research Institute (SwRI) report that data gathered by NASA’s Lunar Reconnaissance Orbiter (LRO) show lighter materials like plastics provide effective shielding against the radiation hazards faced by astronauts during extended space travel. The finding could help reduce health risks to humans on future missions into deep space.

Aluminum has always been the primary material in spacecraft construction, but it provides relatively little protection against high-energy cosmic rays and can add so much mass to spacecraft that they become cost-prohibitive to launch.

The scientists have published their findings online in the American Geophysical Union journal Space Weather. Titled “Measurements of Galactic Cosmic Ray Shielding with the CRaTER Instrument,” the work is based on observations made by the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) on board the LRO spacecraft. Lead author of the paper is Cary Zeitlin (zeitlin@boulder.swri.edu) of the SwRI Earth, Oceans, and Space Department at UNH. Co-author Nathan Schwadron of the UNH Institute for the Study of Earth, Oceans, and Space is the principal investigator for CRaTER.

“This is the first study using observations from space to confirm what has been thought for some time—that plastics and other lightweight materials are pound-for-pound more effective for shielding against cosmic radiation than aluminum," Zeitlin said. "Shielding can’t entirely solve the radiation exposure problem in deep space, but there are clear differences in effectiveness of different materials.”

The plastic-aluminum comparison was made in earlier ground-based tests using beams of heavy particles to simulate cosmic rays. “The shielding effectiveness of the plastic in space is very much in line with what we discovered from the beam experiments, so we’ve gained a lot of confidence in the conclusions we drew from that work,” says Zeitlin. “Anything with high hydrogen content, including water, would work well.”

The space-based results were a product of CRaTER’s ability to accurately gauge the radiation dose of cosmic rays after passing through a material known as “tissue-equivalent plastic,” which simulates human muscle tissue. 

Prior to CRaTER and recent measurements by the Radiation Assessment Detector (RAD) on the Mars rover Curiosity, the effects of thick shielding on cosmic rays had only been simulated in computer models and in particle accelerators, with little observational data from deep space.

The CRaTER observations have validated the models and the ground-based measurements, meaning that lightweight shielding materials could safely be used for long missions, provided their structural properties can be made adequate to withstand the rigors of spaceflight.

Since LRO’s launch in June 2009, the CRaTER instrument has been measuring energetic charged particles— often very heavy and spectacularly energetic particles traveling at nearly the speed of light and cause detrimental health effects—from galactic cosmic rays and solar particle events (SPE's). 

Fortunately, Earth’s thick atmosphere and strong magnetic field provide adequate shielding against these dangerous high-energy particles.

To view the Space Weather article (behind academic pay wall), visit http://onlinelibrary.wiley.com/doi/10.1002/swe.20043/abstract

For more on the CRaTER instrument, visit http://crater.sr.unh.edu/ and for the LRO mission visit http://lunar.gsfc.nasa.gov/mission.html.

CRaTER team at UNH

Related Posts:

Cosmic Ray threat to manned spaceflight tested on MSL (May 31, 2013)

The radiation environment and its effects on human
spaceflight: A Lunar Mission (January 5, 2013)
Cosmic ray flux effects lunar ice (March 19, 2012)
"a perfect storm of cosmic rays" (September 29, 2009)
Cosmic rays and manned space travel (September 16, 2009)
Cosmic ray flux highest ever recorded (September 3, 2009)
Returning to the Moon (August 9, 2009)
LUNAR-TEX radiation blanket: Skeptical (May 11, 2009)
NASA cataract detection down to Earth (January 18, 2009)
NASA and Congress sacrifice radiation shielding flexibility
by removing dry landing hardware (May 17, 2008)

Managing Space Radiation Risk in the New Era of Space Exploration (2008)
Committee on the Evaluation of Radiation Shielding for Space Exploration
National Research Council

GSFC releases LEND lunar water demonstration

Map of energetic neutron absorption near the lunar South Pole, showing the places where water ice is most likely to be found, built up and trapped for aeons in areas of extreme cold and darkness. Interestingly, not all the permanently shadowed regions show strong detection of hydrogen atoms while some areas that do receive at least some sunshine do register such a presence. Note the strong indication at Cabeus, chosen late in the LCROSS mission as its impact target in 2009. [NASA/GSFC/SVS/Roscosmos].

NASA has released a new video, prepared by the Science Visualization Studio (SVS) at Goddard, highlighting the Lunar Exploration Neutron Detector (LEND) and results of data that instrument has built up since it arrived in orbit with the Lunar Reconnaissance Orbiter (LRO) three years ago.

The new SVS video is a popular introduction the role of LEND as part of the LRO mission, not a comprehensive report of results except to show how data was methodically collected over many months in polar orbit.

Though not without some controversy, regarding its resolution and final value, the Russian LEND - a highly anticipated follow-up to Lunar Prospector (1998-1999) - has now orbited over the Moon's north and south poles 18,000 times. The instrument has measured absorption of neutrons scattered from the surface below, indicating the possible presence of water ice or other volatile hydrogen compounds at the Moon's high latitudes.

The press release discussion of the new LEND video reads, "Since the 1960's, scientists have suspected that frozen water could survive in cold, dark craters at the Moon's poles. While previous lunar missions have detected hints of water on the Moon, new data from the Lunar Reconnaissance Orbiter (LRO) pinpoints areas near the south pole where water is likely to exist. The key to this discovery is hydrogen, the main ingredient in water: LRO uses its Lunar Exploration Neutron Detector, or LEND, to measure how much hydrogen is trapped within the lunar soil. By combining years of LEND data, scientists see mounting evidence of hydrogen-rich areas near the Moon's south pole, strongly suggesting the presence of frozen water." 

Related Posts:
LRO LEND: "A Scientific Dispute" (March 27, 2012)
Will LRO LEND prove effective? (February 21, 2012)
Where are the wettest places on the Moon (October 23, 2010)
LRO analysis of LCROSS impact proves essential (October 21, 2010)

LRO LEND: "A Scientific Dispute"

Uncollimated (top) and collimated (below) views of
the Moon from the LEND instrument. From “What
is the LEND collimated detector really measuring,”
Eke et al., 43rd Lunar and Planetary Science
Conference (2012), #2211.

Paul D. Spudis
The Once and Future Moon
Smithsonian Air & Space
 

Attendees at the recently concluded 43rd annual Lunar and Planetary Science Conference had front row seats to a heated debate on new data from the Moon.  As opposed to how many envision scientific debate – coolly logical, white-frocked intellectuals, dispassionately discussing points of contention in a laboratory – what they witnessed was an impassioned and stormy exchange of differing opinions.  There is good reason for passion.  Subsequent decisions based on these data places the success or failure of future missions in the crosshairs.

Point in question: a team of scientists on NASA’s Lunar Reconnaissance Orbiter (LRO) mission claim that their new neutron mapping shows that locations of high hydrogen content are not well correlated with dark areas near the poles of the Moon.  This relation seems to contradict (at least, it is not consistent with) one of the key concepts about water at the poles of the Moon – that it occurs in dark polar cold traps, where water is stable on the surface and cannot be ejected from the Moon (as appears to be the case for most water deposited there).

This new idea is current because LRO carries something called a collimated neutron spectrometer, named the Lunar Exploration Neutron Detector (LEND), an instrument provided to NASA by IKI, the Space Research Institute of the Russian Academy of Science.  NASA flew a neutron spectrometer to the Moon over 10 years ago on a global mapping mission called Lunar Prospector (LP).  That instrument had an omni-directional (4-pi) field-of-view (FOV), meaning that it simultaneously looked in all directions.  As such, the resolution of features on the surface made by this instrument was fairly low, being effectively equal to the altitude of the spacecraft.  The LP neutron mapping spectrometer obtained a best resolution of about 30 km, meaning that any smaller feature could not be resolved in the FOV of the detector.  Unfortunately, most of the dark, cold areas near the poles are smaller than this.  LP detected enhanced levels of hydrogen in both polar regions, but couldn’t detect whether these hydrogen reservoirs were confined to the permanently shadowed areas, thus increasing the likelihood that the hydrogen was in the form of water.

In order to identify zones of high hydrogen content and determine if they were truly associated with the cold, dark areas, as predicted by theory, scientists wanted higher resolution maps of the poles for the next mission to the Moon.  The way to obtain higher resolution is to restrict the field of view of the neutron instrument to where it looks only at a small spot directly below the orbiter.  This involves putting a shield on the detector (called a collimator) that restricts the FOV to the lunar surface only; this technique can resolve areas on the surface smaller than the orbital altitude during mapping.  A drawback to using a collimator is that restricting the FOV means that the flux, or total number of neutrons that can be detected per unit time, is much lower, which greatly reduces precision of the measurements.  However, the longer the counting is conducted, the more precise the data.  LRO was to remain in lunar orbit for at least a two-year mission; it has now been orbiting the Moon and collecting data for almost three years.

Over the last year, the LEND team’s reports have appeared in the scientific literature.  To the surprise of most lunar scientists, their team claimed that in all but two or three isolated cases, hydrogen detected by LEND does not correlate with the polar dark areas.  This puzzling result would seem to indicate that perhaps we do not fully understand the nature of the polar hydrogen and the processes involved in their creation and retention.

Thus the debate commenced at last Monday’s scientific session, when several scientists (I will collectively call them the “skeptics”) who work with neutron data from LP and other missions, differed with the LEND team conclusions, who in turn vigorously defended their results as valid, citing as evidence the coincidence of laser altimetry and neutron data over one crater (Shoemaker) near the south pole of the Moon.  Having studied the LEND data set themselves, the skeptics contended that the actual average count rate for neutrons is less than half of that quoted by the LEND team, meaning that the hydrogen content inferred from the LEND data are significantly less precise than claimed.  Moreover, they estimate that the signal from the collimated (high resolution) detectors is only a few percent of the total signal, whereas the LEND team claims that it is roughly one-third of the total.  The skeptics make the point that if the collimator is working as the LEND team claim, the map derived from the collimated detector should be a sharper, higher resolution version of the low-resolution map made in the uncollimated mode.  In fact, the skeptics contend that the two maps look completely different (see figure at top of this post), suggesting that the collimated product is detecting something else; based on the observed pattern, it is probably related to the amount of iron in the lunar surface.

This is not some arcane, academic dispute.  We will depend on the mapping results from LRO to identify potential landing sites for future missions, including the selection of the most hydrogen-rich areas for exploration and possible future utilization.  Such decisions could involve the expenditure of hundreds of millions of dollars, so there is some pressure to make the correct ones.

So where does this impasse leave the lunar science community?  Mostly befuddled.  The vast majority of scientists simply do not have the time to read every scientific paper published, especially in fields peripheral to their own interests.  However, in the course of their research, scientists often find that they must decide what to believe about uncertain or controversial ideas that may relate to their own studies.  Is there a correct way to decide which interpretation to believe?  After a quick and cursory review of the competing concepts, most scientists will adopt the majority, or “consensus” viewpoint.  If they know someone with relevant expertise, they may ask for and rely on the considered judgment of that expert.  Few scientists are able to read and make their own considered judgments about a field in which they have little understanding or no expertise.  Thus, they tend to choose their position on the basis of non-scientific evaluations of the technical credibility of those arguing for or against a given viewpoint.

In this case, the detailed distribution of hydrogen at the poles of the Moon remains unclear.  While both LP and LEND uncollimated (e.g., omni-directional) maps appear nearly identical, the collimated LEND polar hydrogen maps show widely varying concentrations, with little coherence over short distances.  Repeatability of measurement is important in science.  The fact that two completely different instruments on two different missions found nearly identical results suggests that the low resolution, uncollimated LP and LEND maps are currently the best reflection of reality we have.  These uncollimated data most likely will remain the polar hydrogen maps of choice by working lunar scientists.

Originally published March 27, 2012 at his Smithsonian Air & Space blog The Once and Future Moon, Dr. Spudis is a senior staff scientist at the Lunar and Planetary Institute. The opinions expressed are those of the author and are better informed than average.

Related Post: Will LRO LEND prove ineffective? (February 21, 2012)
 

Cosmic ray flux effects lunar ice

Space scientists from the University of New Hampshire and colleagues report they have quantified levels of radiation on the Moon's surface from galactic cosmic ray (GCR) bombardment that over time causes chemical changes in water ice and can create complex carbon chains similar to those that help form the foundations of life.

The radiation process causes the lunar regolith to optically mature (OMAT), or darken, over time; important in understanding the geologic history of the Moon.

Scientists present their findings online in the American Geophysical Union's Journal of Geophysical Research. "Lunar Radiation Environment and Space Weathering from the Cosmic Ray Telescope for the Effects of Radiation (CRaTER)," is based on measurements made by the CRaTER instrument on-board NASA's Lunar Reconnaissance Orbiter (LRO). 

The paper's lead author is Nathan Schwadron, an associate professor of physics at the UNH Space Science Center within the Institute for the Study of Earth, Oceans, and Space (EOS). Co-author Harlan Spence is the director of EOS and lead scientist for the CRaTER instrument.

The telescope provides the fundamental measurements needed to test our understanding of the lunar radiation environment and shows that "space weathering" of the lunar surface by energetic radiation is an important agent for chemical alteration. CRaTER measures material interactions of GCRs and solar energetic particles (SEPs), both of which present formidable hazards for human exploration and spacecraft operations. CRaTER characterizes the global lunar radiation environment and its biological impacts by measuring radiation behind a "human tissue-equivalent" plastic.

Serendipitously, the LRO mission made measurements during a period when GCR fluxes remained at the highest levels ever observed in the space age due to the Sun's abnormally extended quiet cycle. During this quiescent period, the diminished power, pressure, flux and magnetic flux of the solar wind allowed GCRs and SEPs to more readily interact with objects they encountered -- particularly bodies such as our Moon, which has no atmosphere to shield the blow.

The arrival of cosmic rays at Earth, far more of a threat to survival than solar radiation, more than doubles on average when the Sun is relatively quiet. The peak in neutron flux since 1958 (at right) occurred during the unusually long solar minima 2009-2010, "serendipitously" coincident to the beginning of LRO's mission and the CRaTER instrument on-board [Moscow Neutron Monitor].

"This has provided us with a unique opportunity because we've never made these types of measurements before over an extended period of time, which means we've never been able to validate our models," notes Schwadron. "Now we can put this whole modeling field on more solid footing and project GCR dose rates from the present period back through time when different interplanetary conditions prevailed." This projection will provide a clearer picture of the effects of GCRs on airless bodies through the history of the solar system.

Moreover, CRaTER's recent findings also provide further insight into radiation as a double-edge sword. That is, while cosmic radiation does pose risks to astronauts and even spacecraft, it may have been a fundamental agent of change on celestial bodies by irradiating water ice and causing chemical alterations. Specifically, the process releases oxygen atoms from water ice, which are then free to bind with carbon to form large molecules that are "prebiotic" organic molecules.

In addition to being able to accurately gauge the radiation environment of the past, the now more robust models can also be used more effectively to predict potential radiation hazards spawned by GCRs and SEPs.

Says Schwadron, "Our validated models will be able to answer the question of how hazardous the space environment is and could be during these high-energy radiation events, and the ability to do this is absolutely necessary for any manned space exploration beyond low-Earth orbit."

Indeed, current models were in agreement with radiation dose rates measured by CRaTER, which together demonstrates the accuracy of the Earth-Moon-Mars Radiation Environment Module (EMMREM) being developed at UNH. EMMREM integrates a variety of models describing radiation effects in the Earth-Moon-Mars and interplanetary space environments and has now been validated to show its suitability for real-time space weather prediction.

Will LRO LEND prove ineffective?

Noted "NSR's," or "Neutron Suppression Regions" from LEND measurements over the first two years of the LRO mission clearly show depths associated with areas in and around the permanently shadowed regions of craters Cabeus and, nearer to the lunar South Pole, Shoemaker and, to a lesser extent, Faustini. Haworth, where the LAMP far UV detector seems to have detected frost, shows little if any neutron suppression. Is the presentation of LEND data highly contrasted, in false color, to appear to be of higher resolution? [NASA].

A quiet controversy has surfaced regarding the usefulness of the Russian-built and managed LEND instrument on-board the Lunar Reconnaissance Orbiter, now approaching its 12,300th orbit of the Moon.

Intended as a sharper-resolution follow-up to neutron flux detection performed by Lunar Prospector (1998-1999) a team of investigators representing four prestigious institutions are expressing doubts about the actual resolution of the LEND Collimated Sensors for EpiThermal Neutrons (CSETN).

LRO instrument payload schematic. The LEND package
is at bottom center [NASA].

“Serious questions have been raised concerning the effectiveness of the LEND CSETN for actually returning a sharper map of the lunar neutron flux,” the team writes in “What is LEND collimated detector really measuring?” a presentation prepared for the 43rd Lunar and Planetary Science Conference (2012), in March.

Cosmic rays of a wide range of energies rain in on the inner Solar System from beyond the Sun’s interplanetary magnetic field, at a more or less constant rate that varies by roughly 100 percent to a peak infall from all directions at solar cycle minima and dropping by half inversely to solar cycle max. As these energetic nuclei bombard the lunar surface the result is a predictable flux of freed neutrons scattered into space. As a detector in low lunar orbit passes overhead these newly space borne neutrons can be related to their origin on the lunar surface.

The presence of hydrogen, in the form of hydroxyl molecules, hydrogen gas or was water ice, in the upper half meter of the lunar surface will absorb or refract some of these neutrons. It was the confirmation of such an apparent detection by Lunar Prospector that gradually convinced many scientists of the otherwise thought unlikely presence of cold- trapped volatiles, perhaps in the form of water ice, near the Moon’s highest latitudes.

But the neutron detection array on-board the highly budget-restricted Lunar Prospector was of very low resolution, and though the detection of hydrogen by that instrument was mostly confined to the lunar poles its detection was not confined directly to permanently shadowed regions, the only place where water ice was believed possible. 

The two complementary detectors of the Lunar Exploration Neutron Detector (LEND), flying on LRO, carried high hopes of a great improvement on the Lunar Prospector measurements.  The work by Eke, Teodoro and Lawrence, et al., first appearing in Science last fall, “uses the Lunar Prospector results in combination with data from the LEND CSETN to demonstrate that less than 5 percent of the LEND CSETN counts come from the (detector’s actual) field of view.”

The abstract “What is the LEND collimated detector really measuring,” (LPSC 2012, #2211) can be reviewed HERE.

A preliminary letter responding to similar critical comments from Lawrence, et al., written by LEND team members I.G. Mitrofanov, et al., was published in Science, February 14, 2011. It can be read HERE.

PETA protests target radiation testing

Dave Wedge
Boston Herald

While about two dozen animal rights supporters gathered outside McLean Hospital in Belmont this morning to protest controversial radiation tests on monkeys, researchers defended the testing as adhering to government guidelines.

Wearing T-shirts and holding signs, People for the Ethical Treatment of Animals members voiced their opposition to a NASA project that will zap about 20 squirrel monkeys with radiation. The primates will be hit with radiation doses equivalent to three years of space travel at a New York facility and then will be shipped to McLean to live under the watch of Harvard Medical School researchers.

PETA officials say the testing is cruel because it could lead to cancer, premature aging and cognitive damage in the monkeys. Six PETA protesters donned monkey masks and sat in cages during the peaceful protest.

Follow this story HERE.

NASA to irradiate squirrel monkeys to research long-term exposure in Deep Space

Tom Chivers
Telegraph.UK

"There's a long-standing commitment on the part of NASA to deep space travel and with that commitment comes a need for knowing what kinds of adverse effects deep space travel might have, what are the risks to astronauts. That's not been well assessed.

"The beauty of this is that we can assess at different time points after exposure, so not only do we get a sense of rather immediate effects, but then we can look again at longer time points.

"That kind of information just hasn't been available."

Read the story, HERE.

More on the Skylight at Marius Hills

Terrain Camera on-board JAXA lunar orbiter Kaguya (SELENE-1) captured data formulated into this image showing what appears to be an approximately 65 meter-wide 'Skylight,' extending down at least 90 meters deep among the domes and rima of Marius Hills (12°N, 306°E) in Oceanus Procellarum [ISAS/JAXA/Junichi Haruyama et al.].

Rachel Courtland
New Scientist

A deep hole on the moon that could open into a vast underground tunnel has been found for the first time. The discovery strengthens evidence for subsurface, lava-carved channels that could shield future human colonists from space radiation and other hazards.

The moon seems to possess long, winding tunnels called lava tubes that are similar to structures seen on Earth. They are created when the top of a stream of molten rock solidifies and the lava inside drains away, leaving a hollow tube of rock.

Their existence on the moon is hinted at based on observations of sinuous rilles – long, winding depressions carved into the lunar surface by the flow of lava. Some sections of the rilles have collapsed, suggesting that hollow lava tubes hide beneath at least some of the rilles.

But until now, no one has found an opening into what appears to be an intact tube. "There's sort of a chicken-and-egg problem," says Carolyn van der Bogert of the University of Münster in Germany. "If it's intact, you can't see it."

Finding a hole in a rille could suggest that an intact tube lies beneath. So a group led by Junichi Haruyama of the Japanese Aerospace Exploration Agency searched for these "skylights" in images taken by Japan's Kaguya spacecraft, which orbited the moon for almost two years before ending its mission in June.

Deep cave

The team found the first candidate skylight in a volcanic area on the moon's near side called Marius Hills. "This is the first time that anybody's actually identified a skylight in a possible lava tube" on the moon, van der Bogert, who helped analyse the feature, told New Scientist.

The hole measures 65 meters across, and based on images taken at a variety of sun angles, the the hole is thought to extend down at least 80 meters. It sits in the middle of a rille, suggesting the hole leads into a lava tube as wide as 370 meters across.

It is not clear exactly how the hole formed. A meteorite impact, moonquakes, or pressure created by gravitational tugs from the Earth could be to blame. Alternatively, part of the lava tube's ceiling could have been pulled off as lava in the tube drained away billions of years ago.

Radiation shield

Finding such an opening could be a boon for possible human exploration of the moon. Since the tubes may be hundreds of meters wide, they could provide plenty of space for an underground lunar outpost. The tubes' ceilings could protect astronauts from space radiation, meteoroid impacts and wild temperature fluctuations.

"I think it's really exciting," says Penny Boston of the New Mexico Institute of Mining and Technology in Socorro. "Basalt is an extremely good material for radiation protection. It's free real estate ready to be exploited and modified for human use."
Blocked passage?

But even if astronauts were to rappel into the hole, they might not be able to travel far into the tube it appears to lead into. "I would bet a lot of money that there's a tube there, but I would not bet nearly so much that we could gain access to the tube," says Ray Hawke of the University of Hawaii at Manoa, who has also hunted for lunar lava tubes.

Rubble or solidified lava might block up the tube. "It could be closed up and inaccessible," Hawke told New Scientist.

NASA's Lunar Reconnaissance Orbiter (LRO), which should be able to snap images of the area that are at least 10 times as sharp, could help reveal more about the hole. And more lava tube openings may be found.

The Kaguya team is still combing over images of other areas in search of additional skylights. And Hawke says a proposal is in the works to use LRO's main camera to snap oblique shots of the lunar surface. This could help reveal cave entrances that are not visible in a bird's-eye view.

Radiation-hardening could lighten spacecraft

"The space community is eager to find ways to produce space-hardened microelectronic devices using only everyday commercial chip-making technologies, Cressler says. The savings in cost, size and weight could be very significant.

"Silicon-germanium is a top candidate for this application because it has intrinsic immunity to many types of radiation. The catch is that, like other materials, SiGe cannot stand up to the extremely destructive heavy ions present in galactic cosmic rays. At least, not yet. "

Read the report of work at Georgia State, HERE.

Cosmic rays and manned space travel

Galactic Center as seen from Fermi Telescope (All-Sky, first light, 2008) "Cosmic rays were discovered in 1912 by Victor Hess. He was trying to test the theory that most of the Earth's radioactivity came from the ground, so he took three detectors up to 5300 meters in a hot air balloon, expecting a decrease in the ionization rate. Instead, he found an increase, indicating the primary source of radiation was coming not from below, but from above. Hess thought that he was observing high energy photons, hence the name "cosmic rays." When a cosmic ray strikes a molecule in the atmosphere, it produces a cascade of lighter particles. Initial collisions produce exotic particles like pions, but by the time the shower has reached the ground, these particles have decayed, and we're generally left with several common byproducts -- muons, electrons, neutrons, neutrinos, and gamma rays." (Icecube.wisc.edu) Beyond Earth's atmosphere, at the mercy of the Sun's interplanetary magnetic field and that of Earth, in "deep space," astronauts are assessed individually to determine their risk, over a lifetime, of Radiation Exposure Induced Death, or "REID." When that risk reaches four percent, they are grounded.

Too much radiation for astronauts to make it to Mars

David Shiga
New Scientist

"FORGET the risk of exploding rockets or getting sideswiped by a wayward bit of space junk. Radiation may be the biggest hurdle to human exploration beyond low-Earth orbit and could put a damper on a recently proposed mission to Mars orbit."

Read that story HERE, or...

Joel Raupe
Lunar Pioneer Research Group

Why Norm Augustine’s Review of Human Space Flight committee reportedly included in their report to the President a trip to Phobos, and lingering in Mars orbit twenty years from now, among their possible long-term alternatives to a more immediate return to the Moon is a mystery to us.

Like everyone else we will have to wait for a closer look at the Committee’s final report. This is because the Lunar Pioneers have been echoing conclusions affirmed and reaffirmed by experts over decades, that manned spaceflight beyond our Moon is unlikely to become safe anytime soon without the kinds of technological breakthroughs we believe only frequent travel to the Moon is likely to make possible.

There is no question of our capability of going to Mars, and the Pioneers estimate the trip would not have to be nearly as expensive as estimated. Returning safely from Mars, if by “safely” you mean “alive,” is also very doable. But there is one problem we have yet to learn our way around.

Radiation Exposure Induced Death, or “REID.”

If you want to go to Mars, you will need nuclear energy or something faster and more sustained than your grandfather’s chemical rockets. Otherwise the dangers posed by Galactic Cosmic Rays, or "GCR's," is both real and unavoidable.

One practical kind of shielding might be an 11-meter thick shell of lunar regolith.

This reality was explicitly highlighted in two reports chartered by NASA and delivered by the National Academy of Sciences following President George W. Bush’s establishment of the Vision for Space Exploration as national policy in 2004.

In the very influential "Scientific Context for the Exploration of the Moon" - Final Report (2007), and, in more detail, “Managing Space Radiation Risk in the New Era of Space Exploration” (2008), the Space Studies Board used NASA’s own measure of radiation exposure risk assessment as the gauge, and their conclusions were clear.

Every astronaut is individually assessed, based on their age and lifetime experience, living or flying at high altitudes, or how often they flew using polar routes, etc., and the probabilities are crunched to come up with that person’s own lifetime risk of Radiation Exposure Induced Death, or “REID.” Anytime a prospective space flight is estimated to take an astronaut beyond a 4 percent probability of REID, they are grounded.

In fact, your career is likely over long before reaching a 3 percent lifetime risk of REID.

Interestingly, the older you are, with only a moderate estimated time at high altitude during your lifetime, the lower the REID, because The Great Bird of the Galaxy is going to catch up with you a lot sooner from one of the many "manifold dooms" than when you were a adolescent. The risk is estimated on a cumulative basis, so an individual astronaut’s risk of REID is proportionally lower then if they had traveled in space beginning at a younger age.

Back in the Apollo Era the danger people at home worried about most was presented by the Sun and solar flares, and not without some reason. But the danger we can’t get around when traveling beyond the Moon is not coming from the Sun.

Solar radiation and solar particle events (SPEs) are hazardous to your health, but the kinds of shielding, comparable to hull materials measured in units of aluminum per square centimeter has proven to actually provide a high degree of protection from the Sun’s most common dangers.

The dangerous radiation that concerns scientists today when we talk about deep space travel and human health is far more energetic, even if it is less frequent, immediate, or even apparent to the human eye.

If you had gamma ray eyes, you could see the problem all over the sky, just like the Fermi Telescope launched in 2008; along the band of the Milky Way, from supernovae remnants like the Crab, or a curiously swath with no apparent origin coming at us from the area of sky northeast of Orion. Generally speaking, however, Cosmic rays rain down at us from every possible direction.

Astrobiology magazine discussed the culprit in a quick overview of recent advances in ground-based Cosmic ray shadow detection, and provocatively entitled “Death Rays from Space.”

"Cosmic rays are mostly high-energy protons, with some electrons, positrons and heavy nuclei mixed in. Their energies range over 14 orders of magnitude, with the most energetic cosmic rays flaunting a billion times more energy than is possible in man-made particle accelerators on Earth.

“The current understanding is that most cosmic rays originate in the shock waves that emanate from supernova explosions. We can't precisely trace where a cosmic ray came from because its trajectory is bent by magnetic fields. In fact, a typical cosmic ray will bounce inside the galaxy's magnetic field for millions of years before eventually colliding with something… like Earth.

"Every square centimeter on the top of the Earth's atmosphere is hit by several cosmic rays per second," and, "this is forever going on."

“None of these "primary" cosmic rays ever reach us on the ground. Instead, they collide with atoms in the upper atmosphere, creating a shower of lower energy "secondary" particles.

Secondary effects

“At sea level, the majority of cosmic ray secondaries are highly penetrating muons. About 10,000 muons pass through our bodies every minute. Some of these muons will ionize molecules as they go through our flesh, occasionally leading to genetic mutations that may be harmful.

“At present, the average human receives the equivalent of about 10 chest X-rays per year from cosmic rays. We shouldn't be alarmed by this, since it is just part of the natural background radiation under which humans and our ancestors have been exposed to for eons. Indeed, cosmic-ray-induced mutations may sometimes be beneficial,”

All of which is true, we suppose, if you think in terms only of your species, and never traveling beyond the blue sky. Our best estimates are that every person on-board a vessel traveling to Mars and back, however, using present-day shielding and our best possible speeds, return to Earth with a greater than 4 percent chance of eventually dying of radiation induced death.

To make things tougher, the hull design most likely to shield you from the Sun’s worst punches is very likely to worsen the danger posed by Cosmic rays. A metallic nucleon, atomic Iron or Beryllium, or whatever, would encounter the same degree of Aluminum per square centimeter and immediately become a shotgun spray of secondary and tertiary particles, about the size of your head, and multiplying the genetic risk proportionally.

It takes a lot to stop the highest energy Cosmic rays.

To make things even tougher still, although it is unlikely to last forever, we are presently experiencing the deepest solar minimum since 1913. At solar maximum, when the interplanetary magnetic field is at its greatest strength, incidence of Cosmic rays at Earth is reduced by as much as 60 percent.

Alternatively, we are at the present solar minimum, and after fifty years of monitoring the cosmic ray bombardment here at one-Earth distance from the Sun, we discover that the incidence of Cosmic rays today are at their highest sustained levels ever recorded. The last such peak recorded was of a far shorter duration and happened during the solar minimum of the middle 1960’s.

Obviously, now would not a good time to travel to Mars. So, what about the Moon?

For those who want to go to Mars the problem of REID must be tackled, and the Moon, as always, waits patiently to provide an excellent testing ground, with many necessary materials already in place.

Standing on the Moon, during those three-quarters of a lunar day periods when the Moon is not within trailing field lines of Earth’s magnetic field, half the incoming Cosmic radiation is blocked by the Moon itself, at your feet. To retreat entirely from this radiation would require, some estimate, at least 11 meters of lunar regolith, all around you. This is a difficult, but not impossible, proposition.

Transported through deep space surrounded by 11 meters of lunar quick-crete might seem prohibitive if launched from Earth. But, using rail-gun technology, such a feat might not seem so ridiculous beginning from the Moon.

Like the Moon, Cosmic rays presents the space wanderer with an immovable object,"so high you can't get over it, so low, you can't go under it, so wide, you can't go 'round it... must go through that door."

NLSI picks Goddard to study the Dynamic Moon

NASA's Lunar Science Institute (NLSI) has selected a proposal submitter by NASA Goddard to investigate the influence of the Sun on the Moon. The wide-ranging effects of Solar Wind and its surface interaction with the dusty lunar surface was identified as essential research, by the National Academies of Science's Space Studies Board in 2007, before extended human activity on the Moon can begin.

The award, one of seven announced by NASA, devotes $5 million over four years beginning in April. Researchers will build advanced simulations to explore the interaction between the Sun and Moon, emphasizing surface interactions during solar particle events (SPEs) such as intense flares and Coronal Mass Ejections. The study will also investigate spellation along with both primary and secondary high energy Galactic Cosmic Ray impacts and those of micrometeorites.

"Many people think of the moon as dead, but if you look with a different pair of glasses – at the atomic level – it is very active," said Dr. William Farrell of NASA Goddard, Principal Investigator for the proposal, called the Dynamic Response of the Environment at the Moon (DREAM).

"One of our roles will be to provide modeling support to scientists examining data from NASA's lunar science missions, such as the Lunar Reconnaissance Orbiter (LRO). There are always surprises in science, and our computer models can help them understand unexpected results or choose among competing theories," said Farrell.

"The sun is constantly throwing energy and matter into space – radiation and a million-mile-per-hour stream of electrically charged particles called the solar wind. If you put an object in the path of this stuff, such as the moon, that object will get hit and react. This reaction to inflowing solar matter includes surface erosion of gas and dust. There are also other subtle reactions, like the electrostatic charging of the lunar surface and any object on the surface that can be a concern for human explorers. All these effects are enhanced during a solar storm when the sun temporarily spews out a greater amount of energy and matter," said Farrell.

DREAM researchers will study many ways the sun influences the moon, but some interactions will be of special interest to human explorers: solar storms, the electric charging of lunar dust, and the erosion of potential resources at the poles.

Read the Goddard Press Release HERE.

Danger ahead as the Sun goes quiet

David Shiga
New Scientist

THE sun's ability to shield the solar system from harmful cosmic rays could falter in the early 2020s, just in time to threaten the health of NASA astronauts as they return to the moon.

As well as the 11-year cycle of sunspots and solar flares, the sun's activity experiences longer-term shifts lasting several decades. The sun is currently in a long-term high, having been relatively active for nearly a century, but it is not known when this will end.

To find out, a team led by Jose Abreu of the Swiss Federal Institute of Aquatic Science and Technology in Duebendorf analysed 66 long-term highs from the past 10,000 years, as recorded in fluctuating levels of rare isotopes such as beryllium-10 in ice cores from Greenland. These are produced when cosmic rays break down the nuclei of oxygen and nitrogen atoms in the Earth's atmosphere. Production of these isotopes peaks when the sun is inactive, as the weaker solar wind lets more cosmic rays enter the solar system, which hit the Earth.

Based on the duration of past highs, and the fact that the current one has already lasted 80 years, the team has calculated that its most likely total lifetime is between 95 and 116 years, and they suspect the high will probably end at the shorter end of this range (Geophysical Research Letters, DOI: 10.1029/2008GL035442).

Records of the sun's brightness during the 20th century show that it gets slightly dimmer when it is less active, so could a long-term reduction in activity help to offset global warming? No such luck, says Nigel Weiss from the University of Cambridge, who is a member of Abreu's team. While there is a rough correspondence between a period of very low activity from 1645 to 1715 and the middle of a period of lower average global temperatures lasting from the late 16th to mid 19th century, leading some to suggest a causal link, this correlation could be a coincidence, Weiss says.

Weiss also points out that the sun's brightness changes only slightly with variations in activity. If the sun does dim slightly in the coming decades, he says, this would only reduce the warming expected due to human-induced climate change by 0.1 °C. "It might be discernible, but it would be a blip rather than a major change," he says. "It is nothing [compared] with the global warming that is now being produced through pumping of greenhouse gases into the atmosphere."

Those most likely to be affected would be astronauts. Beyond the Earth's protective magnetic field, their exposure to the increased cosmic rays let into the solar system due to a weaker solar wind could cause cancer and fertility loss. One benefit to astronauts would be a decline in the number of solar flares.

David Hathaway of NASA's Marshall Space Flight Center in Huntsville, Alabama, says the evidence for past lulls is strong, but he is sceptical about the team's attempt to predict the arrival of the next one. "This is a little like trying to predict when someone's winning streak will end," he says. "We know that it will happen, but reliable predictions are virtually impossible."

Cosmic Rays Spark a Renewed Interest in the distant Voyagers

Their data are spread upon an impossibly thin wavefront measured in trillionths of a watt and hardly detectable over the background cosmic fizz. But both Voyagers I & II nevertheless regularly and obediently acknowledge a receipt of commands in a two way communication taking more than a full day to complete, even at the speed of light and after 30 years of hurling away from Earth.

From their remote "outposts," now just barely beyond the electromagnetic dominance of the Sun, these two prides of Pasadena and Dr. Sagan dutifully download basic but increasingly important information about the larger interstellar space we still share.

The Voyager's minimally-funded space weather station reports had been thought to be little more than a novelty after their primary missions were completed and their cameras were powered down. But their renowned robotic patience may finally be drawing some fresh attention sparked by a renewed interest among those intrepid hominids who want to journey beyond Earth's Moon but are confronted with the harsh realities of hard and heavy interstellar radiation.

"Global warming" would probably be welcome relief from the cold of the Kuiper Belt. Back on Earth, however, scholarly studies of a possible role for the secondary particles of Cosmic Rays impacting Earth's atmosphere and possibly playing a role in cloud formation on Earth, affecting albedo and even climate, refuse to go away. Cosmic Rays bombardment had been thought to be constant, except where deflected by our nominally variable star's sunspot cycle.

Both Voyagers are healthy, out there beyond the Termination Shock of the Heliopause, where the interplanetary medium buffets the interstellar depths, and both vehicles continue to send home points of data allowing us an, as yet, under-appreciated, sustained glimpse of Deep Space.

Cosmic Ray have a swinging variability after all, beyond that part of its stream that is moderated by nearby Solar influence, particularly during solar flares and CMEs here in the inner solar system.

Perhaps those who make it their business to follow space weather should add these faithful reports from Voyager to their posts of things like sunspot counts and the speed of solar protons per cubic meter, etc.

Even during the present protracted solar minima, though, the incidence of nucleons out there where the Voyagers travel, heavy ions with punches greater than 50 million electron Volts seems to be at a slump, over the past few months, for example. Even in the long distant night, the Voyagers repeat the oldest message in their lesson books: For every answered question, two more to take its place. The Universe is more than we know.

Does this slight variation in the bombardment of "Galactic Cosmic Rays," or GCR's bring into disrepute beliefs most experts hold that the Cosmic Ray background is steady?

On Earth, the launch last month of GLAST, tuning up now to begin looking for deeper anisotropy to their infall, Cosmic Rays should be "peaking" at an unusually long Solar Minimum. GLAST is just getting started when the "seeing" should be good.

It could only be better out there beyond 100 A.U.'s "Billions and Billions" of kilometers out from under the garish sun.