The lunar forensic files

View of the Moon at gamma-ray wavelengths, as imaged by the Compton Gamma Ray Observatory satellite.  These gamma rays are induced by the collision of cosmic rays with the lunar surface, the same process recently found able to synthesize organic molecules in lunar polar ice deposits [Dave Thompson (NASA/GSFC) et al., EGRET, Compton Observatory].

Paul Spudis

The Once and Future Moon

Smithsonian Air & Space

A recent study indicates that water ice and simple molecules of carbon and nitrogen might form the seed material for more complex substances, some of which might ultimately be involved in the origin of life.  The work from the University of Hawaii took measurements of the levels of cosmic radiation from the Lunar Reconnaissance Orbiter (LRO) and applied it to a composition similar to that observed by the impacting LCROSS probe at the south pole of the Moon.  

As you may recall, this probe found both water vapor and ice particles ejected by the impact in one of the permanently dark regions near the pole; it also observed additional compounds, including methane, ammonia and some other simple organic molecules.  These substances are present in cometary ices and thus, it was thought that their presence could indicate a cometary origin for the Moon’s polar ice.

The new work does not negate that interpretation, but adds complexity to the puzzle by showing that it may be possible to manufacture some of the more complex organic molecules from the simple substances found in cosmic ice, whether deposited from the nuclei of impacting comets or made in place within the cold traps of the lunar poles.  Once again, we find that the polar regions of the Moon are even more interesting scientifically than we had thought.

The generation of new and more complex organic compounds must be a surficial process since material buried at levels deeper than a couple of meters is shielded from even the most energetic cosmic rays.  For this reason, the material observed during the LCROSS impact is likely of cometary origin because most of the ejecta created by that impact comes from depths of a few meters.  While material in the lunar surface is overturned by impact gardening, such overturn is extremely slow (rates of overturn below about 1 meter depth occur on timescales of greater than 1 billion years, the same timescale on which this radiation-induced production occurs).

The generation of complex organic molecules is an important topic of research for the origin of life.  Most scientific strategies focus on the search for extraterrestrial life in more Earth-like environments, such as a previously warmer and wetter Mars or in the hypothesized deep oceans of Europa.  A few studies have focused on the physical processes of organic chemistry, specifically the generation of complex molecules in space, within small bodies such as cometary nuclei and on primitive planetary surfaces, such as the polar deposits of the Moon and Mercury.  Findings to date show that complex organic substances are generated in a variety of environments and under a variety of energetic conditions.

Because they date from early in Solar System history and contain the materials needed for living systems (water and organic matter), comets have long been thought to be the seedbeds of life.  Comets are remnants of the original solar nebula, the cloud of debris out of which our Solar System formed.  At a certain position and beyond in the nebula, water is stable in solid form (the so-called “frost line”); in our Solar System, the frost line is between the orbits of Jupiter and Mars.  Water in nebular material inside this line vaporized and was dissipated by the solar wind, some blown outward and some disassociated by ultraviolet radiation.  But water outside of the frost line can condense into ice particles, which then may be accreted into planetary objects.  The smallest and most water-rich of these objects are the comets, most of which originate far beyond the frost line in the most distant regions of our Solar System (the so-called “Oort cloud”).  Larger icy objects in the outer Solar System include the satellites of the Jovian planets, which are predominantly made of water ice with minor amounts of admixed rocky material.  The inner (terrestrial) planets such as Earth and Mars are made mostly of rocky material but contain minor amounts of water, a consequence of their incorporation of cometary material during assembly and subsequent impact bombardment.

This last process operates on the Moon as well.  Because the Moon represents a stable, unchanging environment over billions of years, it accumulates the evidence and detritus of the impact history of that era.  Most of the volatile component of this impacting debris is lost from the Moon, but any of it that becomes trapped in the cold, dark areas near the poles remains there forever.  The poles of the Moon are thus a natural laboratory for the study of one of the early processes in Solar System history – the creation of complex organic substances from the more primitive and simple elements and compounds.  In this sense, the pre-biotic organic chemistry of the lifeless and barren Moon serves the cause of the study of life’s processes and origin.

As we continue to study the Moon, we find that it offers much more than one might suspect at first glance.  The Moon’s early history reveals the secrets of planetary assembly, impact bombardment, global melting and differentiation into core, mantle and crust.  Its middle history tells us about the thermal evolution of planets, as internal heat spawned the volcanism that resurfaced part of the Moon and operates on all of the terrestrial planets.  The continued impact history recorded in the Moon’s surface layer documents a phase of Earth history missing from our terrestrial geological record, including the possibility of episodic waves of impacts that are at least partly responsible for extinctions of life recorded in the fossil record.  This same surficial layer also records the history and output of our Sun, the provider of energy to the planets and the principal driver of climate change on Earth.  The interconnections between the various branches of lunar science with the other sciences grow more evident and more significant over time.

This new research makes the recently renewed interest in the value of the Moon and new lunar missions more comprehensible.  Far from being a mere echo of some previous space glory, a return to the Moon to undertake new scientific studies, new exploration and to develop a wholly new set of technologies impacts all of space science and exploration in many different and unexpected ways.  Insights into the origins of life can come from detailed examination of lunar polar volatiles.  These same materials can also enable travel to more distant destinations and open up Earth-Moon space to economic development.  In both cases, lunar return will enable and facilitate our understanding and movement into space.

As my colleague David Lawrence of APL put it, “One of the take-homes is, go back to the moon and look.  Dig up samples, see what’s there.”  Sound advice.

Related:

Proton flux and radiation dose from galactic cosmic rays in the lunar regolith
and implications for organic synthesis at the poles of the Moon and Mercury

Crites, Lucey & Lawrence

Icarus, Vol. 226, No. 2, Nov.–Dec. 2013, pg. 1192–1200

Live CRaTER data from LRO re-broadcast as music (January 14, 2014)

More from CRaTER on radiation health hazards (November 19, 2013)

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

Earth and Moon share primal water source (May 10, 2013)

"Our view of the Moon has turned upside down" (April 26, 2012)

Cosmic ray flux effects lunar ices (March 19, 2012)

The Moon's metallic water (February 27, 2011)

LRO analysis of LCROSS data proves essential (October 21, 2010)

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

Clementine - The Legacy, Twenty Years On

Engineering model of the Clementine spacecraft in the Lunar Exploration Vehicles exhibit at the National Air and Space Museum. Interstage and solid rocket motor (bottom half) was discarded before insertion into lunar orbit.

Paul D. Spudis

The Once and Future Moon

Smithsonian Air & Space

The first spacecraft to globally map the Moon left lunar orbit on May 3, 1994.  Clementine, a joint Department of Defense-NASA mission, had systematically mapped the Moon’s surface over 71 days, collecting almost 2 million images.  For the first time, scientists could put results of the Apollo lunar sample studies into a regional, and ultimately, a global context.  Clementine collected special data products, including broadband thermal, high resolution and star tracker images for a variety of special studies.  But in addition to this new knowledge of lunar processes and history, the mission led a wave of renewed interest in the processes and history of the Moon, which in turn, spurred a commitment to return there with both machines and people.  We peeked into the Moon’s cold, dark areas near the poles and stood on the edge of a revolution in lunar science.

Prior to Clementine, good topographic maps only existed for areas under the ground tracks of the orbital Apollo spacecraft.  From Clementine’s laser ranging data, we obtained our first global topographic map of the Moon.  It revealed the vast extent and superb preservation state of the South Pole-Aitken (SPA) basin and confirmed many large-scale features mapped or inferred from only a few clues provided by isolated landforms.  Correlated with gravity information derived from radio tracking, we produced a map of crustal thickness, thereby showing that the crust thins under the floors of the largest impact basins.

Two cameras (with eleven filters) covered the spectral range of 415 to 1900 nm, where absorption bands of the major lunar rock-forming minerals (plagioclase, pyroxene and olivine) are found.  Varying proportions of these minerals make up the suite of lunar rocks.  Global color maps made from these spectral images show the distribution of rock types on the Moon.  The uppermost lunar crust is a mixed zone, where composition varies widely with location.  Below this zone is a layer of nearly pure anorthosite, a rock type made up solely of plagioclase feldspar (formed during the global melting event that created the crust).  Craters and large basins act as natural “drill holes” in the crust, exposing deeper levels of the Moon.  The deepest parts of the interior (and possibly the upper mantle) are exposed at the surface within the floor of the enormous SPA basin on the far side of the Moon.

Topographic map of the Moon made from Clementine laser altimetry in mid-latitudes and stereo images near the poles. Large depression in southern far side is the South Pole-Aitken basin.

Clementine showed us the nature and extent of the poles of the Moon, including peaks of near permanent sun-illumination and crater interiors in permanent darkness.  From his first look at the poles, Gene Shoemaker (Leader of the Clementine Science Team) got an inkling that something interesting was going on there.  Gene was convinced that water ice might be present, an idea about which I had always been skeptical.  At that time, no trace of hydration had ever been found in lunar minerals and the prevailing wisdom was that the Moon is now and always had been bone dry.  With Gene arguing to keep an open mind and Stu Nozette (Deputy Program Manager) devising a bistatic radio frequency (RF) experiment to use the spacecraft transmitter to “peek” into the dark areas of the poles, we moved ahead on planning the observations.

To my astonishment (and delight), a pass over the south pole of the Moon showed evidence for enhanced circular polarization ratio (CPR) – a possible indicator of the presence of ice.  A control orbit over a nearby sunlit area showed no such evidence.  However, CPR is not a unique determinant for ice, as rocky, rough surfaces and ice deposits both show high CPR.  It took a couple of years to reduce and fully understand the data, but collection of the bistatic collection was successful.  In part, our ice interpretation was supported by the discovery of water ice at the poles of Mercury (a planet very similar to the Moon).  We published our results in Science magazine in December 1996, setting off a media frenzy and a decade of scientific argument and counter-argument about the interpretation of radar data for the lunar poles (an argument that continues to this day, despite subsequent confirmation of lunar polar water from several other techniques).

Along with Clementine’s success came a growing interest in lunar resources and a new appreciation for the complexity of the Moon.  This interest led to the selection of Lunar Prospector (LP) as the first PI-led mission of NASA’s new, low-cost Discovery series of planetary probes.  LP flew to the Moon in 1998 and carried instruments complementary to the data produced by Clementine, including a gamma-ray spectrometer to map global elemental composition, magnetic and gravity measurements, and a neutron spectrometer to map the distribution of hydrogen.  LP found enhanced concentrations of hydrogen at both poles, again suggesting that water ice was probably present.  The debate on the abundance and physical nature of the water ice continued, with estimates ranging from a simple enrichment of solar wind implanted hydrogen in polar soils, to substantial quantities of water ice trapped in the dark, cold regions of the poles.

Buttressed by this new information, the Moon became an attractive destination for robotic and human missions.  With direct evidence for significant amounts of hydrogen (regardless of form) on the surface, there now was a known resource that would support long-term human presence.  This hydrogen discovery was complemented by the identification in Clementine images of several areas near the pole that remain sunlit for substantial fractions of the year – not quite the “peaks of eternal light” first proposed by French astronomer Camille Flammarion in 1879 but something very close to it.  The availability of material and energy resources  – the two biggest necessities for permanent human presence on the Moon – was confirmed in one fell swoop.  Combined, the results of Clementine and LP finally gave scientists the Lunar Polar Orbiter mission we had long sought.  These two missions certified the possibility of using lunar resources to provision ourselves in space, permanently establishing the Moon as a valuable, enabling asset for human spaceflight.  Remaining was to verify and extend the radar results from Clementine and map the ice deposits of the poles.

The Clementine bistatic experiment led to the development of an RF transponder called Mini-SGLS (Space Ground Link System), which flew on the Air Force mission MightySat II in 2000.  This experiment miniaturized the RF systems necessary for a low mass, low power imaging radar.  With the 2008 inclusion of our Mini-SAR on India’s Chandryaan-1 lunar orbiter, we finally got the chance to build and fly such a system.  Chandrayaan-1 not only mapped the high CPR material at both poles, it also carried a spectrometer (the Moon Mineralogy Mapper, or M3) that discovered large amounts of adsorbed surface water (H2O) and hydroxyl (OH) at high latitudes.  Coupled with the measurement of exospheric water above the south pole by its Moon Impact Probe, Chandrayaan-1 significantly advanced our understanding of polar water, revealing it to be abundant and present in more varied forms on the Moon than had previously been imagined.

Mosaic of Clementine images of the south pole of the Moon. Dark regions contain water ice and small areas near pole are sunlit for significant fractions of the lunar day.

The ever increasing weight of evidence for the presence of significant amounts of water at the lunar poles led to the LCROSS experiment being “piggybacked” on NASA’s 2008 Lunar Reconnaissance Orbiter (LRO) mission.  LCROSS was a relatively inexpensive add-on, designed to observe the collision of the LRO launch vehicle’s Centaur upper stage with the lunar surface, looking for water in the ejecta plume of that impact.  Water in both vapor and solid form was observed, suggesting the presence of water ice in the floor of the crater Cabaeus (at concentration levels between 5 and 10 weight percent).  LRO orbits the Moon and collects data to this day.  Although much remains unknown about lunar polar water, we now know for certain that it exists; such knowledge has completely revised our thinking about the future use and habitation of the Moon.

The Clementine programmatic template has influenced spaceflight for the last 20 years.  The Europeans flew SMART-1 to the Moon in 2002, largely as a technology demonstration mission with goals very similar to those of Clementine.  NASA directed the Applied Physics Laboratory (APL) to fly Near-Earth Asteroid Rendezvous (NEAR) to the asteroid Eros in 1995 as a Discovery mission, attaining the asteroid exploration opportunity missed when control of the Clementine spacecraft was lost after leaving the Moon.  India’s Chandrayaan-1 was of a size and payload scope similar to Clementine.  The selection of LCROSS as a low-cost, fast-tracked, limited objectives mission further extended use of the Clementine paradigm.

The “Faster-Better-Cheaper” mission model, once panned by some in the spaceflight community, is now recognized as a preferred mode of operations, absent the emotional baggage of that name.  A limited objectives mission that flies is more desirable than a gold-plated one that sits forever on the drawing board.  While some missions do require significant levels of fiscal and technical resources to attain their objectives, an important lesson of Clementine is that for most scientific and exploration goals, “better” is the enemy of  “good enough.”  Space missions require smart, lean management; they should not be charge codes for feeding the beast of organizational overhead.  Clementine was lean and fast; perhaps we would have made fewer mistakes had the pace been a bit slower, but overall the mission gave us a vast, high-quality dataset, still extensively used to this day.  The Naval Research Laboratory transferred the Clementine engineering model to the Smithsonian in 2002.  The spacecraft hangs today in the Air and Space Museum, just above the Apollo Lunar Module.

It is probably not too much of an exaggeration to say that Clementine changed the direction of the American space program.  After the failure of SEI in 1990-1992, NASA was left with no long-term strategic direction.  For the first time in its history, NASA had no follow-on program to Shuttle-Station, despite attempts by Dan Goldin and others to secure approval for a human mission to Mars (then and now, a bridge too far – both technically and financially).  This programmatic stasis continued until 2003, when the tragic loss of Columbia led to a top-down review of U.S. space goals.  Because Clementine had documented its strategic value, the Moon once again became an attractive destination for future robotic and human missions.  The resulting Vision for Space Exploration (VSE) in 2004 made the Moon the centerpiece of a new American effort beyond low Earth orbit.  While Mars was vaguely discussed as an eventual (not ultimate) objective, the activities to be done on the Moon were specified in detail in the VSE, particularly with regard to the use of its material and energy resources to build a sustainable program.  Regrettably, various factors combined to subvert the Vision, thereby ending the strategic direction of America’s civil space program.

Clementine was a watershed, the hinge point that forever changed the nature of space policy debates.  A fundamentally different way forward is now possible in space – one of extensibility, sustainability and permanence.  Once an outlandish idea from science fiction, we have found that lunar resources can be used to create new capabilities in space, a welcome genie that cannot be put back in the bottle.  Americans need to ask why their national space program was diverted from such a sustainable path.  We cannot afford to remain behind while others plan and fly missions to understand and exploit the Moon’s resources.  Our path forward into the universe is clear.  In order to remain a world leader in space utilization and development – and a participant in and beneficiary of a new cislunar economy – the United States must again direct her sights and energies toward the Moon.

Note: Background history for the Clementine mission is described in a companion post at my Spudis Lunar Resources blog, HERE.

Originally published 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 but are better informed than average.

Some Related Posts

LOLA: Cabeus (LCROSS)

Not all "permanently shadowed regions," or "PDR's," on the Moon are created equal. Not long prior to the LCROSS impact (near the center of the permanently shadowed interior of Cabeus crater, in the LROC Wide Angle Camera (WAC) monochrome mosaic seen above) this nearside crater was discovered to be perhaps the "juiciest" spot on the Moon. At the same time craters further south, closer to the Moon's south pole (and presumably more completely and "permanently shadowed," were dryer. Some of these regions, deep and adjacent to one another showed very different "volatile profiles." And just as Lunar Pioneer seemed to show with far less resolution of data, late in the last century, "volatiles" like water molecules show a profile in wider areas that are not permanently shadowed. Repeated orbital passes by LRO's laser altimeter (LOLA) have now brought this shadowed area to light in detail [NASA/GSFC/Arizona State University].

Goddard Space Flight Center, June 15 - On October 9, 2009, the Lunar Crater Observing and Sensing Satellite (LCROSS) impacted a permanently shadowed region in Cabeus Crater near the Moon's South Pole. Since then, data from LRO and LCROSS have revealed the presence of volatiles, including water, in Cabeus. This LOLA image shows details of the region within Cabeus that cannot be seen in visible imagery (due to the aforementioned permanent shadow). LRO's polar orbit allows for a high density of measurements near the Moon's poles, which in turn gives us high-resolution data of the lunar polar topography.

View LOLA Archives, HERE.

The Moon's metallic water

The LCROSS Shepherding Spacecraft Mid-Infrared Camera (MIR) captured this false-color image of the Centaur impact ejecta plume about 20 seconds after impact, October 9, 2009 [NASA/ARC/LCROSS].

Bill Steigerwald
NASA Goddard

Bring a filter if you plan on drinking water from the moon. Water ice recently discovered in dust at the bottom of a crater near the moon's south pole is accompanied by metallic elements like mercury, magnesium, calcium, and even a bit of silver. Now you can add sodium to the mix, according to Dr. Rosemary Killen of NASA's Goddard Space Flight Center in Greenbelt, Md.

Recent discoveries of significant deposits of water on the moon were surprising because our moon has had a tough life. Intense asteroid bombardments in its youth, coupled with its weak gravity and the Sun's powerful radiation, have left the moon with almost no atmosphere. This rendered the lunar surface barren and dry, compared to Earth.

However, due to the moon's orientation to the Sun, scientists theorized that deep craters at the lunar poles would be in permanent shadow and thus extremely cold, and able to trap volatile material like water as ice if such material were somehow transported there, perhaps by comet impacts or chemical reactions with hydrogen, a major component of the solar wind.

The October 9, 2009 impact of NASA's Lunar CRater Observation and Sensing Satellite (LCROSS) spacecraft into the permanently shadowed region of the Cabeus crater confirmed that a surprisingly large amount of water ice exists in this region, along with small amounts of many other elements, including metallic ones.

Read the full feature, HERE.

LRO-Diviner Lunar Radiometer observations of cold traps in the Moon’s south polar region

David A. Paige,1* Matthew A. Siegler,1 Jo Ann Zhang,1 Paul O. Hayne,1 Emily J. Foote,1 Kristen A. Bennett,1 Ashwin R. Vasavada,2 Benjamin T. Greenhagen,2 John T. Schofield,2 Daniel J. McCleese,2 Marc C. Foote,2 Eric DeJong,2 Bruce G. Bills,2 Wayne Hartford,2 Bruce C. Murray,3 Carlton C. Allen,4 Kelly Snook,5 Laurence A. Soderblom,6 Simon Calcutt,7 Fredric W. Taylor,7 Neil E. Bowles,7 Joshua L. Bandfield,8 Richard Elphic,9 Rebecca Ghent,10 Timothy D. Glotch,11 Michael B. Wyatt,12 Paul G. Lucey13

22 OCTOBER 2010 VOL 330 SCIENCE

Diviner Lunar Radiometer Experiment surface-temperature maps reveal the existence of widespread surface and near-surface cryogenic regions that extend beyond the boundaries of persistent shadow. The Lunar Crater Observation and Sensing Satellite (LCROSS) struck one of the coldest of these regions, where subsurface temperatures are estimated to be 38 kelvin. Large areas of the lunar polar regions are currently cold enough to cold-trap water ice as well as a range of both more volatile and less volatile species. The diverse mixture of water and high-volatility compounds detected in the LCROSS ejecta plume is strong evidence for the impact delivery and cold-trapping of volatiles derived from primitive outer solar system bodies.

The Moon’s polar regions are notable because of their potential to cryogenically trap water ice and other volatile species (1). The Lunar Reconnaissance Orbiter (2) (LRO) Diviner Lunar Radiometer Experiment has been mapping the infrared emission from the Moon since July 2009 using seven spectral channels that span a wavelength range from7.55 to 400 mmat a spatial resolution of ~200 m (3).

Thermal maps of the south polar region (Fig. 1, A and B) were obtained during the LRO monthly mapping cycle just before the Lunar Crater Observation and Sensing Satellite (LCROSS) impact (4), as the Moon approached southern summer solstice (5). The mapped quantity is the bolometric brightness temperature, which is the wavelength-integrated radiance in all seven Diviner channels expressed as the temperature of an equivalent blackbody (6). For quantifying the overall heat balance of the surface and comparing with available models, the bolometric brightness temperature is the most fundamental and interpretable measurable quantity.

For the simplest case in which Diviner’s surface footprint is filled with a blackbody of uniform surface temperature, the bolometric brightness temperature will be equal to the temperature of the surface.

Figure 1. Maps of measured and model-calculated surface and subsurface temperatures in the lunar south polar region. The outer circle on all maps is 80° south latitude. Observations were acquired between 6 September and 3 October 2009 as the Moon approached southern summer solstice. (A) Diviner-measured daytime bolometric brightness temperatures acquired between 11.4 and 13.6 hours local time (5). (B) Diviner-measured nighttime bolometric brightness temperatures acquired between 21.41 and 1.66 hours local time (5). (C) Model-calculated annual average near-surface temperatures and the location of the LCROSS impact in Cabeus Crater. (D) Model-calculated depths at which water ice would be lost to sublimation at a rate of less than 1 kg/m−2 per billion years. - The white regions define the locations where water ice can currently be cold trapped on the surface, the colored regions define the upper surface of the lunar ice permafrost boundary and the gray regions define locations where subsurface temperatures are too warm to permit the cold-trapping of water ice within 1 m of the surface.

In the more general case, where Diviner’s surface footprint contains small-scale slopes, shadows, or rocks, the brightness temperatures in Diviner’s individual infrared channels may vary with wavelength depending on the distribution of sub–footprint-scale temperatures, spectral emissivities, and photometric properties. In this case, the bolometric brightness temperature cannot be interpreted in terms of a unique surface temperature. However, within cold regions that are not in direct sunlight, simultaneously acquired brightness temperatures in Diviner channels 7 (25 to 41 mm), 8 (50 to 100 mm), and 9 (100 to 400 mm) are in good agreement (6), which is consistent with uniformly high spectral emissivity across this wavelength range and relatively uniform temperatures within each Diviner footprint (fig. S1, A and B). This interpretation is supported by the results of an analysis of data acquired in each of the Diviner infrared channels at the LCROSS impact site in Cabeus Crater (7). For unilluminated regions, we use Diviner bolometric brightness temperatures as reasonably accurate proxies for the temperature of the surface.

The thermal maps show that the coldest regions are located on the floors of larger impact craters that receive no direct sunlight (Fig. 1,A and B). For these regions, previous modeling studies have shown that the main heat source is emitted infrared radiation from distant interior sunlit crater walls (8–11). Topographic relief within cold crater floor regions can provide additional radiation shielding, resulting in intensely cold localized regions with measured mid-day bolometric brightness temperatures as low as 29 K. Heat flow fromthe lunar interior may contribute to the overall heat balance of these coldest surfaces, but is not dominant compared to heating from scattered solar and infrared radiation during this season (6). Diviner’s summer solstice observations represent a valuable snapshot of the south polar region surface temperatures that can be extended in depth and in time with models. We have developed a thermal model that realistically accounts for the effects of large-scale topographic relief on direct and indirect solar and infrared radiation on the heat balance of the lunar surface (6). The model uses a ~500-m-scale triangular mesh based on south polar topography derived from the Kaguya LALT laser altimeter (12) and a spatially uniform set of thermal and reflectance parameters that are generally consistent with those derived from previous studies (6). The excellent overall agreement between maps (fig. S3, A and B) and histograms (Fig. 2A) of the observed and calculated bolometric temperatures demonstrate the general validity of our modeling approach. The only notable discrepancy occurs for daytime temperatures in the shadowed portions of craters that have measured bolometric temperatures in the range of 60 to 120 K, where the model underestimates temperatures by roughly 15 K (fig. S4, A and B). This may be largely due to directionally anisotropic infrared emission from rough sunlit crater walls, which is not accounted for in the present model (6). Given the better agreement between the model and the Diviner nighttime data, we estimate that the net effect on model-calculated annual average temperatures at 2-cm depth (Figs. 1C and 2B) is less than 7 K in the warmest craters and close to zero in the coldest craters. For the limiting case of zero heat flow from the lunar interior, the temperatures at greater depths would be close to this near-surface average temperature (11). However, with nonzero heat flow, average temperatures will increase with depth at a rate proportional to the heat flow rate and inversely proportional to the thermal conductivity. Using parameters derived from the heat flow experiments at the Apollo 15 and 17 landing sites (13), we estimate that LCROSS impact site temperatures at 2-m depth should be <6 K higher than annual average surface temperatures (fig. S5). Although the Diviner bolometric temperatures presented here and cooling curves at the LCROSS impact site are generally consistent with the presence of unconsolidated regolith near the surface (7, 14), the thermophysical properties of the Moon’s cryogenic regolith are not currently well constrained and could differ substantially from those in warmer regions (15), particularly at depth.

Figure 2. (A) Normalized histograms of measured daytime and nighttime bolometric brightness temperatures for the maps shown in Fig. 1, A and B, with comparisons to model-calculated surface temperatures at the same locations and times as those of the Diviner observations (fig. S3, A and B). (B) Histograms of model-calculated annual average temperatures at 2-cm depth for the maps shown in Fig. 1C and fig. S7, A to D, and at the LCROSS impact site for selected values of qmax, the mean maximum angle between the Moon’s spin axis and the normal to the ecliptic plane. qmax =1.54° for present-day conditions. (C) The recent evolution of qmax as a function of the Earth-Moon distance (29). (D) The volatility temperatures of a range of potential cold-trapped volatile compounds (21, 22) View higher-resolution Fig. 2 HERE.

We expect that the Moon’s cryogenic regions extend to depths of at least tens of meters below the surface, but estimating the volumetric extent of the Moon’s cryogenic regions purely from surface-temperature observations is highly uncertain.

Thermal model results can be used to estimate the stability of water ice deposits to loss by sublimation and diffusive migration through the lunar regolith (11, 16). Figure 1D shows a map of the depths at which water ice would be lost at a rate of less than 1 kg m−2 per billion years, which corresponds to a loss rate of 1 mm per billion years for a pure ice deposit (6). The results show that surface cold traps for water ice are surrounded by much more extensive “lunar permafrost” regions where water ice is stable in close proximity to the surface (17). These regions may receive direct solar radiation during periods when solar lighting conditions are most favorable, but maintain annual maximum temperatures at depth that are sufficiently cold to effectively prevent appreciable water loss due to sublimation. Because of their more hospitable surface thermal and illumination environments, lunar permafrost regions may be accessible locations for future in situ exploration of the Moon’s cold traps.

The overall picture painted by the present thermal state of the lunar south polar region is one of extreme cold. Temperatures in the Moon’s larger cold traps are closer to those expected for the poles of Pluto (18) than for Earth’s closest neighbor. At the cold temperatures that exist within most south polar craters, cold-trapped water molecules have negligible mobility (16), such that any water molecules deposited on the surface will not effectively diffuse below the surface where they can be protected from loss processes such as photolysis and sputtering (19). In cryogenic regions, burial of frozen volatiles by impact gardening is likely to be a much more effective process (20). However, warmer permafrost regions that currently exist at the margins of cold traps may represent somewhat more favorable environments for the downward diffusion of water molecules into the regolith, which should be aided by the daytime temperature gradient between warmer surface layers and colder subsurface layers below.

The distribution of temperatures in the lunar south polar region also places constraints on the thermal stability of non-water volatile species. Figure 2D shows the volatility temperatures (the temperatures at which pure solids exposed to vacuum at the surface would sublimate at a rate of 1 mm per billion years) for several volatile species (21, 22). Non-water subsurface volatiles will also be stable to sublimation at higher temperatures owing to the effects of diffusive migration through the regolith (6). Large areas of the lunar south polar region have the capability to cold-trap water and less volatile species such as mercury and sodium. All three of these volatile species were in the LCROSS ejecta plume (4, 14, 23).

Colder surface and subsurface areas in the south polar region also have the capability to cold-trap so-called super volatile species that have higher volatility than water, which include compounds such as sulfur dioxide, carbon dioxide, formaldehyde, ammonia, and methanol. The detection of a representative cross-section of these same supervolatile species in the LCROSS ejecta plume (4) represents strong evidence for the impact delivery of volatiles to the Moon by primitive outer solar system bodies, and the subsequent cold-trapping of these volatiles at the lunar poles (21, 22).

A question of interest regarding the lunar cold traps is whether they contain abundant deposits of nearly pure water ice such as those discovered by radar observations of impact craters at the poles of Mercury (24). Diviner-measured summer solstice daytime and nighttime surface bolometric brightness temperatures of 46.7 and 38.7 K in the region surrounding the LCROSS impact site, and model-calculated annual average temperatures at this site at a depth of 2 cm, are close to 38 K (6). As shown in Figs. 1, C and D, and 2B, the LCROSS impact site is a surface cold trap for water and is among the coldest locations in the south polar region. The Lunar Prospector Neutron Spectrometer (LPNS) results show that the average hydrogen abundance in the near-surface regolith at the south pole is ~70 parts per million (ppm) by weight, which translates to a water-equivalent average abundance of ~600 ppm by weight (25). Our results show that the surface and near-surface water ice cold traps comprise >66% of the surface area poleward of 85° south latitude (Fig. 1D). If we assume that all the hydrogen detected by LPNS was uniformly distributed within these cold traps, then the average water-equivalent abundance would be only ~1000 ppm by weight, which is substantially less than the 1 to 10% water content inferred at the LCROSS impact site (4). This suggests that the LCROSS site must be enriched in water compared to the average south polar near-surface cold trap, which is consistent with enhanced hydrogen abundances observed in the Cabeus region by orbital neutron spectrometers (26–28).

The spin pole of the Moon is currently in a tidally damped Cassini State 2 configuration in which the time-averaged maximum angle between theMoon’s spin axis and the normal to the ecliptic plane (qmax) has decreased to its present value of qmax = 1.54° as the Earth-Moon distance increased over time (Fig. 2C) (29). The absolute time scale for the tidal evolution of the Earth-Moon system is highly uncertain, but it is likely that the transition depicted in Fig. 2C has occurred over a period of more than 1 billion years (30). Model-calculated annual average near-surface temperatures qmax = 4°, 8°, 12°, and 16° (Fig. 2B and fig. S7, A to D) show that portions of the Moon’s south polar region cooled considerably as the Moon’s orbital radius increased, first creating cold traps capable of cold-trapping water, and then trapping compounds with higher volatility. The LCROSS impact site,which is located on the floor of the large Cabeus impact crater, is typical of the coldest areas on the Moon today. However, earlier in the Moon’s orbital history, when qmax was greater than ~10°, the floors of large-impact craters were not the coldest areas on the Moon because the walls of these relatively shallow craters did not shield their floors from direct solar radiation. Based on the results in Fig. 2B and fig. S7, A to D, the Moon’s earliest surviving near-surface cold traps are not located on the floors of large-impact craters, but rather on the floors of intermediate-sized craters, which thus may have had longer opportunities to accumulate water ice.

1Department of Earth and Space Sciences, University of California, Los Angeles, 595 Charles E. Young Drive East, Los Angeles, CA 90095, USA. 2Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA. 3California Institute of Technology, Pasadena, CA 90025, USA. 4NASA Johnson Space Center, Houston, TX 77058, USA. 5NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA. 6U.S. Geological Survey, Flagstaff, AZ 86001, USA. 7Oxford University, Oxford OX1 3PU, UK. 8University of Washington, Seattle, WA 98195, USA. 9NASA Ames Research Center, Moffett Field, CA 94035, USA. 10University of Toronto, Toronto, ON M5S 3B1, Canada. 11State University of New York, Stony Brook, NY 11794, USA. 12Brown University, Providence, RI 02912, USA. 13University of Hawaii, Honolulu, HI 96822, USA.

*To whom correspondence should be addressed. E-mail: dap@moon.ucla.edu

References and Notes:

1. K. Watson, B. C. Murray, H. Brown, J. Geophys. Res. 66, 3033 (1961).
2. G. Chin et al., Space Sci. Rev. 129, 391 (2007).
3. D. A. Paige et al., Space Sci. Rev. 150, 125 (2010).
4. A. Colaprete et al., Science 330, 463 (2010).
5. The LRO orbit plane is inclined 90° to the lunar equator and is fixed in inertial space. LRO’s ground track rotates through 360° of longitude every sidereal month, allowing Diviner to make one daytime and one nighttime map every 27.3-day mapping cycle in pushbroom nadir mapping mode. Local time on the Moon can be expressed in hours by normalizing the angular distance between geographic longitude and the longitude of the solar point to a 24-hour day. We define daytime to be between 6 a.m. and 6 p.m. local time, and nighttime to be between 6 p.m. and 6 a.m. local time. Because the plane of the LRO orbit rotates relative to the lunar terminator by 360° every Earth year, the local times of Diviner’s observations drift by ~2 hours during each mapping cycle. The subsolar latitude on the Moon currently varies by approximately T1.54° over the course of the Moon’s 346-day draconic year, resulting in distinct seasonal temperature variations at the highest latitudes. The LRO launch date was chosen so that the LRO orbit plane was within 10° of the noon-midnight plane during LRO’s first southern summer solstice.
6. Supporting material is available on Science Online.
7. P. O. Hayne et al., Science 330, 477 (2010).
8. R. R. Hodges, Lunar Planet Sci. Conf. 11, 2463 (1980).
9. D. A. Paige, S. E. Wood, A. R. Vasavada, Science 258, 643 (1992).
10. A. P. Ingersoll et al., Icarus 100, 40 (1992).
11. A. R. Vasavada et al., Icarus 141, 179 (1999).
12. H. Araki et al., Science 323, 897 (2009).
13. M. G. Langseth et al., Proc. Lunar Sci. Conf. 7, 3143 (1976).
14. P. H. Schultz et al., Science 330, 468 (2010).
15. G. J. Taylor et al., Proceedings of Space Resources Roundtable VI. LPI Contribution No. 1224., Golden, CO, Abstract 6040 (Lunar and Planetary Institute, Houston, TX, 2004).
16. N. Schorghofer, G. J. Taylor, J. Geophys. Res. 112, E02010 (2007).
17. We estimate that the total area of surface water ice cold traps in the lunar south polar region shown in Fig. 1D is 13,087 km2, and the total area of near-surface water ice cold traps to a depth of 1 m is 119,507 km2.
18. C. J. Hansen, D. A. Paige, Icarus 120, 247 (1996).
19. T. H. Morgan, D. E. Shemansky, J. Geophys. Res. 96 (A2), 1351 (1991).
20. D. H. Crider, R. R. Vonrak, Adv. Space Res. 31, 2293 (2003).
21. J. A. Zhang, D. A. Paige, Geophys. Res. Lett. 36, L16203 (2009).
22. J. A. Zhang, D. A. Paige, Geophys. Res. Lett. 37, L03203 (2010).
23. G. R. Gladstone, Science 330, 472 (2010).
24. J. K. Harmon, Space Sci. Rev. 132, 307 (2007).
25. W. C. Feldman et al., J. Geophys. Res. 106 (E10), 23,231 (2001).
26. D. J. Lawrence et al., J. Geophys. Res. 111, E08001 (2006).
27. R. C. Elphic et al., Geophys. Res. Lett. 34, L13204 (2007).
28. I. Mitrofanov et al., Lunar Planet. Sci. Conf. 41, 2250 (2010).
29. W. R. Ward, Science 189, 377 (1975).
30. B. G. Bills, R. D. Ray, Geophys. Res. Lett. 26, 3045 (1999).
31. We thank the many people at the Jet Propulsion Laboratory and the Goddard Space Flight Center who contributed to the success of the Diviner instrument and the LRO project. We also thank the National Aeronautics and Space Administration for funding this investigation.

Supporting Online Material
www.sciencemag.org/cgi/content/full/330/6003/479/DC1
Methods Figs. S1 to S7
References 1 February 2010; accepted 12 August 2010 10.1126/science.1187726

Surprising gas from LAMP

From Lunar Pioneer Album 3 -

Southwest Research Institute's LRO/LAMP website, redirected from LRO's main site at Goddard Space Flight Center, remains virtually unchanged since before the launch of LRO, and it's public website (if you can find it) refers to operations in the future. The "Soon" in the "Coming Soon!" above is characteristic of a genuine "ghost site."

EDITOR'S NOTE & OPINION: Out of deep respect for the outstanding, cutting-edge work accomplished by the Southwest Research Institute (SwRI), and because of their contribution to the success of the on-going mission of the Lunar Reconnaissance Orbiter, we're pleased to post the following news release, related to the journal Science publishing research related to the impact of the LCROSS mission, one year ago.

However, of all the experiments and teams contributing to the LRO mission, launched at a huge cost to the American taxpayer, we would be remiss in not expressing our deep displeasure with an apparent complete lack of public outreach by those operating the Lyman-Alpha Mapping Project (LAMP). Of all the LRO instruments, only one other has been more disrespectful of the wider community of proponents of lunar exploration. Only the CRaTER project, whose long publicized website at Boston University has simply disappeared, has done a worse job of keeping the public informed as to their progress.

The Southwest Research Institute's outreach has, since long before LRO/LCROSS was launched on June 18, 2009, kept tantalizing messages posted online advertising features "coming soon," for example, that never arrive, and the team's public information stewardship receives a a failing grade equal at least to that deserved by Boston University and the CRaTER experiment team.

Of all the LRO experiment public outreach efforts, that of the Lunar Reconnaissance Orbiter Camera (LROC) has alone been outstanding, and they deserve to be highly commended.

The Lunar Orbiter Laser Altimeter (LOLA) public information guardians tried, for a time, to make a solid effort and unfortunately also dropped the ball. An LOLA "Image of the Week" feature has now not been undated since the middle of July, in a ridiculous state of affairs, a mocking feature posted on the NASA and GSFC primary LRO public websites.

Diviner and the Mini-RF teams have at least made the effort of keeping citizen-scientists updated, without promising more than they could deliver, and when delivering data products, delivering solid reports. The Russian Institute of Science LEND mission has made results available at least with publicly available monographs and reports.

We take great exception with the presumption expressed by the constant silence out of the Southwest Research Institute and to their apparent contempt for the those interested in the results of their part in the landmark mission of the LRO.

- Joel Raupe
Raleigh, North Carolina

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"LRO's LAMP ultraviolet spectrograph observes
LCROSS blast, detects surprising gases in impact plume"

San Antonio — Oct. 21, 2010 — NASA's Lunar Reconnaissance Orbiter (LRO) and its sophisticated suite of instruments have determined that hydrogen, mercury and other volatile substances are present in permanently shaded soils on the Moon, according to a paper published today in Science.

The Lunar Crater Remote Observation and Sensing Satellite (LCROSS), which launched with LRO, was intentionally crashed onto the Moon's surface Oct. 9, 2009, while LRO instruments watched. About 90 seconds after LCROSS hit the Moon, LRO flew past the debris plume raised by the impact, while the Lyman Alpha Mapping Project (LAMP) and other instruments collected data. Using these data, LAMP team members eventually confirmed the presence of the gases molecular hydrogen, carbon monoxide and atomic mercury, along with smaller amounts of calcium and magnesium, also in gas form.

"We had hints from Apollo soils and models that the volatiles we see in the impact plume have been long collecting near the Moon's polar regions," says Dr. Randy Gladstone, LAMP acting principal investigator, of Southwest Research Institute in San Antonio. "Now we have confirmation."

The point of impact was the Cabeus crater near the lunar south pole. The tiny tilt of the Moon's rotation axis allows the floors of craters near the poles to be permanently shaded from direct sunshine. Without sunlight, temperatures in these areas can be as low as 35 to 100 Kelvin (degrees above absolute zero) – so cold that almost all volatiles that find their way there become trapped. Ongoing micrometeorite impacts cover them with dirt, further isolating them from exposure and possible escape.

LRO's findings are valuable to the future consideration of robotic and manned Moon base locations. Just as the poles have nearby crater floors with permanently shaded regions because of the Moon's orientation to the Sun, they also have nearby mountains and crater rims that are in nearly perpetual sunlight, which would enable the placement and operation of solar-powered systems and equipment. The discovery of water-ice and other resources in the region could also reduce the need to transport resources from Earth for use by astronauts.

"The detection of mercury in the soil was the biggest surprise, especially that it's in about the same abundance as the water detected by LCROSS," says Kurt Retherford, LAMP team member, also of SwRI. "Its toxicity could present a challenge for human exploration."

Developed by Southwest Research Institute, LAMP uses a novel method to peer into the darkness of the Moon's permanently shadowed regions. The ultraviolet spectrograph observes the nightside lunar surface using light from nearby space (and stars), which bathes all bodies in space in a soft glow. This Lyman-alpha glow is invisible to human eyes, but visible to LAMP as it reflects off the Moon. Analyses of the emissions, in collaboration with other LRO instruments, help determine lunar surface properties.

Following the LCROSS impact observations, LAMP continues its investigation of the ultraviolet reflectance properties and composition of the lunar surface and the composition of the lunar atmosphere. Since the conclusion of a one-year reconnaissance mission under NASA's Exploration Systems Mission Directorate, the Science Mission Directorate has assumed oversight of more in-depth investigations for the science instruments. During the science investigation, LAMP will shift into more detailed evaluations of the Moon's atmosphere and its variability.

The paper, "LRO-LAMP Observations of the LCROSS Impact Plume," by G.R. Gladstone, D.M. Hurley, K.D. Retherford, P.D. Feldman, W.R. Pryor, J.-Y. Chaufray, M. Versteeg, T.K. Greathouse, A.J. Steffl, H. Throop, J.W. Parker, D.E. Kaufmann, A.F. Egan, M.W. Davis, D.C. Slater, J. Mukherjee, P.F. Miles, A.R. Hendrix, A. Colaprete, and S.A. Stern, was published in the Oct. 22 issue of Science.

LCROSS flight operations report

Impact Science Observations. The above diagram is a timeline of instrument data collection covering the five minutes prior to the impact of the LCROSS Shepherding Spacecraft. Label `A” shows downlink fully subscribed; `B” shows irregular ticks that reflect images dropped onboard because of downlink "over-subscription;" `C” shows the effect of a ground command sent to reduce camera sampling rates; `D” shows how a command sent to change an image exposure setting enabled imaging the Centaur crater in near-infrared (NIR).

The left image is the near-infrared spectrometers field-of-view just after the Centaur impact.

Paul D. Tompkins, et.al.
Stinger Ghaffarian Technologies
LCROSS Lead Flight Director, ARC

LCROSS (Lunar CRater Observation and Sensing Satellite) was conceived as a low-cost means of determining the nature of hydrogen detected at the polar regions of the moon. The mission presented several inherent challenges – planning for and achieving a precise impact at a lunar pole, guiding a Centaur upper stage far beyond its operational lifetime, co-launching as a secondary payload with the LRO spacecraft, and preparing for and operating such a mission under a highly constrained budget and short development cycle. Beyond these, the flight itself presented other hurdles in the path to success, including several anomalies, one of which was nearly mission-catastrophic.

Section I (of the AIAA report) provides the reader with background on the LCROSS project and components. Section II provides an overview of the flight mission. The remaining sections describe specific challenges encountered in planning and executing the mission and how they were overcome. The paper concludes by highlighting the key factors for the mission’s success.

Managed, partially developed, and operated from NASA Ames Research Center (ARC), LCROSS was selected under the Exploration Systems Mission Directorate’s (ESMD’s) Lunar Precursor Robotic Program (LPRP) as a secondary payload manifested with the Lunar Reconnaissance Orbiter (LRO), under a $79 million cost cap.

LCROSS was designated as a Class D mission, indicating NASA’s willingness to accept greater levels of programmatic and operational risk. Rather than incur the high cost and mission complexity associated with landing at a lunar pole, LCROSS precisely guided its Centaur Earth Departure Upper Stage (EDUS) to a lunar target as a kinetic impactor to raise a plume of polar regolith from the surface. After releasing the Centaur, the guiding Shepherding Spacecraft (S-S/C) employed a suite of nine science instruments to analyze the impact flash and plume materials at close range. Earthbased and orbiting assets, including LRO and the Hubble Space Telescope, acted in a supporting role for impact observations.

The LCROSS project remained on-budget and on-schedule, despite many programmatic and technical challenges. LCROSS launched with LRO on June 18, 2009, and on October 9, 2009, after 112 days in flight, the LCROSS team successfully delivered both the Centaur and S-S/C on-target within Cabeus crater and collected extensive data from all instruments during and after the Centaur impact.

After one month of post-impact analysis, the LCROSS science team announced the positive identification of water on the floor of Cabeus.

The LCROSS mission was faced with many challenges. Late-breaking predictions of possible Centaur gas leaks forced the operations team to revise or newly develop and test broad-reaching procedures and command sequences in the weeks prior to launch. Strict impact targeting precision requirements were made more challenging under the many perturbations to the LCROSS orbit, including from the spacecraft’s own (attitude control) thruster firings and volatiles escaping from the ice-laden Centaur exterior. LCROSS experienced two challenges to propellant reserves - a persistent Centaur gas leak and a propellant-intensive response to a very brief IRU fault. The LCROSS mission operations team, only barely large enough to staff the busy first week of flight, was taxed further by a series of anomalies that, while recoverable, stretched working hours well beyond original expectations.

Read the report (pdf), HERE.

SpaceOps 2010
Huntsville, 25-30 April 2010

LSF 2010 Registration Deadline is July 12

NOTE: Registration for the 3rd Annual Lunar Science Forum (LSF) will close at 5:00 p.m. on Monday, July 12.

Registration is separate from abstract submission, so please make sure you have registered for the Forum. Registration is free and can be completed by following the link on the Lunar Science Forum website:http://lunarscience2010.arc.nasa.gov/

The NASA Lunar Science Institute (NLSI) is pleased to announce the 3rd annual NASA Lunar Science Forum, to be held July 20-22, 2010, at the NASA Ames Conference Center, Moffett Field, California.

This year's forum will feature sessions on scientific results from the Lunar Reconnaissance Orbiter (LRO) and Lunar Crater Observation and Sensing Satellite (LCROSS), as well as the Annual Shoemaker medal and associated keynote lecture. As in past years, science sessions are structured to report on both recent results and future opportunities for lunar science, education and outreach.

The conference will review the state of knowledge of, and opportunities for science:

Of the Moon: Study the nature and history of the Moon (including research on lunar samples) to learn about this specific object and thereby provide insights into the evolution of our solar system.

On the Moon: Investigate the effects of the lunar environment on terrestrial life and the equipment that supports lunar inhabitants, and the effects on the lunar environment of robotic and human presence.

From the Moon: Use the Moon as a platform for performing scientific investigations, including observations of the Earth and other celestial phenomena that are uniquely enabled by being on the lunar surface.

Sessions are structured to report on recent results and anticipate future opportunities for lunar science. Presentations on elements of education and public outreach are included to better understand how lunar exploration can be used to stimulate public interest in space exploration and improve science literacy.

Catch up on details, HERE.

Water and More: An Overview of LCROSS Impact

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The LCROSS spacecraft entering thermal vacuum testing at Northrup Grumman in 2008. Months after the LCROSS impact in October, Anthony Colaprete and other LCROSS investigators will present additional details of science results at next week's 41st annual Lunar and Planetary Science Conference in Texas.

Colaprete, et.al., and the LCROSS Team, NASA Ames Research Center, The Citadel, University of California Santa Cruz, Brown University, University of Idaho and University of Texas at Austin

Introduction: Interest in the possible presence of water ice on the Moon has both scientific and operational foundations. It is thought that a variety of processes could be contributing to the accumulation of water within polar cold traps, including impacts of comets and meteorites, the reaction of solar protons with lunar soil to form water, and outgassing from the moon’s interior. One possible process involves the migration of water in the Moon’s exosphere though ballistic trajectories with eventual capture of these molecules in persistently shadowed polar cold traps. Recent discoveries of a veneer of hydroxyl and adsorbed water in sunlit regions of the moon may support this process [1,2,3]. The form and amount of water presumably associated with the hydrogen concentrations at the poles, as observed by Lunar Prospector (LP) and Lunar Reconnaissance Orbiter (LRO) may represent one end-state in the chain of processes that involve water on the moon. The LCROSS mission’s goal was to identify the source of the elevated hydrogen at the poles and provide a ground truth with regards to the total concentration. Verification of the form and amount of hydrogen can constrain models of the impact history of the lunar surface and the effects of meteorite gardening, photo-dissociation, and solar wind sputtering. With the combined observations of LCROSS, LRO and others it is possible to evaluate the global water distribution and provide a quantitative basis for studies of the Moon’s history and a test of current theories on the form and distribution of lunar hydrogen [4].

Figure 1. The LCROSS Payload Observation Deck and its eight nadir viewing instruments (an additional solar occultation spectrometer is to the side).

Figure 2. Image of the LCROSS impact ejecta cloud as seen in the visible context camera. Inset shows the ejecta cloud expanding to fill the shadowed region targeted at the bottom of the crater Cabeus [NASA/ARC].

The LCROSS Mission: The primary objective of the Lunar Crater Observation and Sensing Satellite (LCROSS) was to confirm the presence or absence of water ice at the Moon’s South Pole. This mission used a 2300 kg kinetic impactor with more than 200 times the energy of the Lunar Prospector (LP) impact. The impact was achieved by steering the launch vehicle’s spent Centaur upper stage into a permanently shadowed polar region. The Centaur is guided to its target by a Shepherding Spacecraft (S-SC), which after release of the Centaur, flew toward the impact plume, sending real-time data and characterizing the morphology, evolution and composition of the plume with a suite of cameras and spectrometers (Figure 1). The last S-SC image and spectrum was timestamped at ~1.9 seconds prior to its impact, at a altitude of approximately 5 km from the lunar surface.

Impact Target: The specific impact site for LCROSS depended on the exact launch date for LRO. The launch date of June 18, 2009 resulted in a 112 day cruise and an impact at the South Pole on October 9. The impact site was selected based on a number of requirements including solar illumination of ejecta, association with observed hydrogen, visibility to earth, and target properties (e.g., slopes and roughness). The targeting capability of the LCROSS S-S/C, ~1 km (3s), allowed for a precise selection of impact point. In the original plan the final target selection was to be made 30 days prior to impact. It was at this point Cabeus A was selected. However, a that time, because the LCROSS trajectory did not require an anticipated trajectory correction, the final targeting maneuver was pushed off to two weeks prior to impact. This extra time was important as it allowed further consideration of LRO observations, coordination with LRO to observe the impact, and verification of LCROSS instrument health closer to the actual impact time. These considerations resulted in a move of the target from Cabeus A to Cabeus. The principle rational for this move was significant level of confidence, both in LP and LRO data, that the Cabeus target held significant amounts of hydrogen.

The Impact: On October 9, 2009 at approximately 11:31:19 UTC the Centaur impacted within about 150 meters of the planned target. The impact resulted in an ejecta cloud that was observed to expand to over 10 km across and to a height of more than 1 km above the surface (Figure 2). All instruments on the LCROSS SSC performed well and a wealth of data was collected.

All portions of the impact, including the flash, ejecta curtain and resulting crater, were observed. From the data set the presence of water was confirmed as was the presence of several other volatile species. In this presentation an overview of the results will be presented.

References: [1] Pieters et al., (2009) Science 326, pp. 568, [1] Pieters et al., (2009) Science 326, pp. 568. [2] Clark (2009), [3] Sunshine et al (2009), [4] Lucey (2000), Proc. SPIE Vol. 4137, 84-88.

From the 41st Lunar and Planetary Science Conference (2010), SPECIAL SESSION: A NEW MOON: LCROSS, CHANDRAYAAN, AND CHANG’E-1 RESULTS, Tuesday, March 2, 2010

What Happened on Impact Night?

Paul D. Tompkins
LCROSS Flight Directors Blog

"The LCROSS mission was ultimately focused on the final four minutes of flight, starting at the time of the Centaur impact, and ending with the impact of the Shepherding Spacecraft. During that time, the Payload Engineer and the Science Team took operational center stage. Once the science payload was powered on, the team’s job was to confirm the full functionality of the instruments, and then to adjust instrument settings to make sure the data we received was the best it could possibly be. For Impact, there were no second chances – the Shepherding Spacecraft was to be destroyed as a forgone outcome of its observation of the Centaur lunar collision."

Read the latest Post HERE.

PSI's Feldman 'delighted' LCROSS confirms Lunar Prospector findings

When the LCROSS rocket stage slammed into Cabeus October 9, creating an impact plume of material possibly not seen in sunlight for billions of years, it conclusively proved that water ice exists in the dark recesses of the moon's polar craters.

The LCROSS findings delighted William Feldman, a senior scientist at the Tucson-based Planetary Science Institute. "What got me excited is that everything we said is right, which is a nice feeling."

In 2001, Feldman was the lead author on a paper in the Journal of Geophysical Research entitled Evidence for Water Ice Near the Lunar Poles, which was based on neutron spectrometer data that he and his instrument team gathered during NASA's 1998 Lunar Prospector mission. Feldman was working at Los Alamos National Laboratory at the time, and came to PSI in 2006.

The paper's conclusions were subsequently confirmed by an extensive series of computer simulations conducted by David Lawrence, of the Johns Hopkins University Applied Physics Laboratory, and his co-workers. This work was published in the Journal of Geophysical Research in 2006.

As early as 1961, scientists speculated that water ice could be hidden in the deep recesses of lunar polar craters that never see daylight. These are some of the coldest spots in the solar system, and water from comet and meteorite impacts could freeze and remain for billions of years.

Researchers using radar on the 1994 Clementine spacecraft thought they saw signatures for water in their data, but the results were controversial, especially when others, using Earth-based radar, found similar signatures in measurements taken near the moon's mid-latitude regions, which are exposed to sunlight.

Feldman and his team didn't measure water directly, but their data showed evidence for inordinately large amounts of hydrogen in some craters. Other phenomena, such as the solar wind and outgassing could account for relatively high levels of hydrogen, "but there was a sufficient amount in some of these craters that it would be hard to understand if it came only from the solar wind or through other processes," Feldman said. "So in our paper we didn't call it 'evidence for hydrogen,' but 'evidence for water'."

Not everyone agreed, and some controversy surrounded the paper. But, when NASA went looking for water on the moon with LCROSS, it ultimate targeted Cabeus which Feldman's Lunar Prospector team identified as having the strongest hydrogen signature among surveyed polar craters.

"This is a big, permanently shaded crater," Feldman said. "In fact, you can't even see it from the Earth because it has a rim that hides it. It takes a satellite to see it."

"When we converted the hydrogen signal to the amount of water ice in the regolith, we found that it was only about 1.5 percent by weight," Feldman added. "That's the reason the radar researchers really couldn't see it. There aren't large enough deposits of high-grade water ice to create the signal needed to identify ice with radar."

So it turns out that Feldman and the Lunar Prospector team showed the first experimental evidence for water on the moon, which has now been conclusively confirmed by the LCROSS mission.

"There's a lot of interest in water on the moon right now," Feldman said. "And there is more to be learned. The whole story is not in yet."

This image, taken by The LCROSS Shepherding and Sensing Satellite's visible-light camera shows the ejecta plume from the LCROSS Centaur stage about 20 seconds after impact [NASA/ARC/LCROSS].

LEAG Premium Presentations are now online

Ina ("D" Formation - (18.5°N, 5.3°E)), an enigmatic formation long the focus of study from the ground and from lunar orbit, was prominent in a presentation by Marc Robinson of the Lunar Reconnaissance Orbiter Camera (LROC) team at Arizona State University, to the 2009 Annual Meeting of the Lunar Exploration Analysis Group (LEAG) in Houston, last month. While many poster and many of the submitted science presentations were made available before the meeting the much anticipated invited presentations were posted to the web just in the past few days.

Chief among these, of course, were up-to-date reports, not yet available anywhere else, from the investigating teams participating in both the LCROSS and LRO projects.

We will continue to look these over, and plan to post further comments about what they contain over the next few days. At this point, though, we 're happy to confirm that each whets the appetite for the expected release to the Planetary Data System of a large part of the data collected using LRO in February 2010 [NASA/GSFC/ASU/LEAG].

Those presentations, brought to our attention by LEAG chair Clive Neal of Notre Dame can be downloaded HERE. (A discussion of Ina, three kilometers across along the straight part of the "D" as seen above and what may be an extinct caldera, is worth reading at Charles A. Wood's LPOD, HERE).