An update on the ARTEMIS twins

Following three years in lunar orbit ARTEMIS P1 and P2 are in excellent condition. Originally in Earth orbit, both spacecraft have been in lunar orbit since the summer of 2011 and in space since February 2007  [UC Berkeley].

Jasper Halekas
Acting Deputy Principal Investigator ARTEMIS
Space Physics Research Group
Space Sciences Lab
University of California at Berkeley

For those of you who aren't familiar with ARTEMIS, (the Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon's Interaction with the Sun mission) is an on-going "mission of opportunity," utilizing two of the original five-spacecraft heliophysics constellation THEMIS mission, "re-tasked" to study the interaction of the Moon and it's space plasma environment. 

The two ARTEMIS spacecraft have now been in elliptical equatorial orbits around the Moon since 2011 and continue to operate flawlessly. Both probes are in very stable orbits, and the health of the spacecrafts and all instruments remains very good.

A sample of the elaborate year-long transfer of the two "re-tasked" THEMIS probes from Earth orbit to lunar orbit. ARTEMIS P1 was the first spacecraft navigated to, and performing station-keeping operations around, the Earth-Moon L1 and L2 Lagrangian points [UC Berkeley].

Current ARTEMIS lunar investigations are focusing on measuring pickup ions from the exosphere, the electrostatic charging of the surface, the plasma wake, and the interaction of the solar wind with remanent crustal magnetic anomalies. ARTEMIS also uses lunar orbit as a platform to observe the solar wind and (around full Moon) the distant terrestrial magnetotail.

More details on recent studies can be found HERE.

With the LADEE mission about to enter its nominal science orbit, and LRO placing new emphasis on its own measurements of the lunar exosphere, ARTEMIS plays a key role by providing complementary measurements of the solar and terrestrial plasma that acts as both a source and sink for the lunar exosphere, affecting dust released from the lunar surface. Together, these three missions team together to measure the inputs, dynamics, and outputs of the coupled system formed by the Moon's surface, its dusty exosphere and the space environment.

All ARTEMIS data is publicly available on a few-day time scale, and we welcome participation from the community. More information on the mission, instrumentation, data (including summary plots), software, etc. is available from http://artemis.ssl.berkeley.edu, or by contacting the team directly.

Related Posts:

Several NASA spacecraft track energy through space (September 26, 2013)

Electric Moon jolts the solar wind (June 2, 2012)

Can we re-purpose space assets? (March 19, 2012)

NASA still studies advantage of lunar resources (February 15, 2012)

Then there were five... in lunar orbit (January 5, 2012)

Twin ARTEMIS probes to study Moon in 3D (July 15, 2011)

ARTEMIS P1 successfully enters lunar orbit (July 1, 2011)

"Dead spacecraft walking" (October 28, 2010)

YouTube demonstration of the re-routing of the two retired THEMIS orbiters to their new bonus mission in lunar orbit.

Scientific Preparations for Lunar Exploration Workshop

Notional (2010) node of the International Lunar Network (ILN) NASA/MSFC

ESA Conference Bureau

We are pleased to announce, on behalf of the organisers, that the Scientific Preparations for Lunar Exploration Workshop will take place on 6 and 7 February 2012 at ESA/ESTEC, Noordwijk, The Netherlands.

Objective: The objective of the workshop is to explore the scientific challenges associated with enabling future exploration of the Moon and the ways in which these challenges can be addressed through:

       - Terrestrial research activities
       - Experiments in Low Earth Orbit and in reduced/micro gravity
       - Investigations on in situ precursor missions

Call for papers
Authors are kindly invited to submit their abstract by using the online abstract submission form, posted on the workshop website http://www.congrex.nl/lunarexplorationws/

More relevant information can be found on the above mentioned website.

We are looking forward to welcoming you at ESA/ESTEC.

Did Earth start out with two moons?

Did Earth, for some protracted period in its earliest history, have "two moons?" Too be precise, for the largely held view of our Moon's origin to be fact, the Moon must once have had many, many of those planetesimals, through fairly rapid accretion, becoming one. A suggestion just published in the science journal Nature posits the origin of our present Moon's farside highlands, and many of its aspects reflecting a lack of uniformity, may have their origins in a primeval collision between two progenitor moons. This possibility may also explain the relative size of our Moon and Earth, among the rocky terrestrial planets. And while were setting our imaginations on a new, unrestrained course, who knows? One of those two moons might have had. at least for a time, a substantial atmosphere [NASA/JAXA].

Forming the lunar farside highlands by accretion of a companion moon

Jutzi & Asphaug
Nature 476, 69–72 (04 August 2011)

The most striking geological feature of the Moon is the terrain and elevation dichotomy¹ between the hemispheres: the nearside is low and flat, dominated by volcanic maria, whereas the farside is mountainous and deeply cratered. Associated with this geological dichotomy is a compositional and thermal variation^{2, 3}, with the nearside Procellarum KREEP (potassium/rare-earth element/phosphorus) Terrane and environs interpreted as having thin, compositionally evolved crust in comparison with the massive feldspathic highlands. The lunar dichotomy may have been caused by internal effects (for example spatial variations in tidal heating⁴, asymmetric convective processes⁵ or asymmetric crystallization of the magma ocean⁶) or external effects (such as the event that formed the South Pole/Aitken basin¹ or asymmetric cratering⁷). Here we consider its origin as a late carapace added by the accretion of a companion moon. Companion moons are a common outcome of simulations⁸ of Moon formation from a protolunar disk resulting from a giant impact, and although most coplanar configurations are unstable⁹, a ~1,200-km-diameter moon located at one of the Trojan points could be dynamically stable for tens of millions of years after the giant impact¹⁰. Most of the Moon’s magma ocean would solidify on this timescale^{11, 12}, whereas the companion moon would evolve more quickly into a crust and a solid mantle derived from similar disk material, and would presumably have little or no core. Its likely fate would be to collide with the Moon at ~2–3 km s⁻¹, well below the speed of sound in silicates. According to our simulations, a large moon/Moon size ratio (~0.3) and a subsonic impact velocity lead to an accretionary pile rather than a crater, contributing a hemispheric layer of extent and thickness consistent with the dimensions of the farside highlands^{1, 13} and in agreement with the degree-two crustal thickness profile⁴. The collision furthermore displaces the KREEP-rich layer to the opposite hemisphere, explaining the observed concentration^{2, 3}.