As we approach the launch of NASA's LRO and LCROSS lunar probes--coming up in just a few hours, we have an excellent excuse to look back on some of the other recent spacecraft that have visited Earth's off-shore island. Bernand Foing--the Project scientist for Europe's SMART-1 lunar probe, the Executive Director for the International Lunar Exploration Working Group (ILEWG), and a wonderful friend to the X PRIZE Foundation--recently shared some of his thoughts on the relationship between these new missions launching today (knock on wood) and the SMART-1 mission from the first half of this decade. Writing to the ILEWG mailing list, Bernard relayed some answers to questions he's getting asked frequently these days.
How did SMART-1 help prepare for LRO and LCROSS?
The SMART-1 mission tested new propulsion and miniaturisation technologies. It also provided some data helping for future lunar exploration and human expeditions. The SMART-1 instruments delivered images and spectral analysis on sites of interest for scientific studies or exploration. Over more than one year, SMART-1 studied illumination daily variations at the poles, and identified peaks of quasi-eternal light that could be used for future robotic outposts and international lunar bases. In addition, SMART-1 X-ray and infrared instruments gave information on lunar elemental and mineral resources. Finally, the SMART-1 impact observation campaign could be used as 'dry run' for the LCROSS water detection observation campaign.
SMART-1 has been a precursor for the Robotic Village and the International Lunar Base that have been advocated by the International Lunar Exploration Working Group (ILEWG). LRO will extend this at much higher spatial resolution with an extensive set of cameras, instruments and techniques to deliver the data needed for preparing safely future human expeditions.
Do you believe there is water ice at the poles? If so, do you believe it is uniformly spread, or secluded in small pockets?
I would expect the water ice could come in thin layers separated by layers of covering protective dust layers. The ice thickness would vary with the history of bombardment of comets and water rich asteroids, but also could come in patches on the surface.
How could it have stayed frozen inside shadowed craters, without sublimating into the lunar exosphere?
Layers at colder temperatures than 80 degrees Kelvin would take billion of years to sublimate, if protected early enough from sputtering by meteorites or from energetic solar wind particles.
What have the Lunar Prospector, Chandrayaan-1, and Kaguya missions found that supports or casts doubt on the theory of lunar ice?
The theoretical prediction for lunar ice comes from studies by Watson (1961) and Arnold (1979). Lunar Orbiter IV showed already areas of permanent shadow, later imaged by Clementine and SMART-1. Clementine found anomalous bistatic radar reflection that may be interpreted as surface ice or surface roughness. Lunar Prospector detected an enhancement of H content in polar areas that could be due to trapping of comet ice (up to 1% mixed with soil) or solar wind Hydrogen. Kaguya did not find extensive surface deposits in the bottom of Shackleton crater that seems to be too warm to host extensive surface ice.
How LRO and LCROSS will further inform us on the possibility of lunar ice?
LRO camera will provide 1m resolution picture enabling to characterize future sites. LRO altimeter, diviner and Lyman alpha mapper will be able to see beyond the visible into permanently shadowed areas and to search for ice deposits. Chandrayaan-1 and LRO radars will search for near-subsurface water ice. Therefore the open question on lunar ice could be sorted soon. LCROSS impact will be a key to search and characterise the ice even buried under the dust.
The next challenge for future missions will be to land in the permanently shadowed bottom of a polar crater and extract a few meters core of soil, possibly sampling at once hundred layers of comets (or water rich asteroids) that impacted the Moon in the past 3 billion years!
What is Europe doing about lunar exploration and future landers?
After the SMART-1 development, operations and data analysis, ESA has been involved in Chang?E1 Chinese lunar mission, and contributed 3 instruments to Indian Chandrayaan-1 lunar orbiter, still delivering new data. ESA studied lunar polar lander with objectives to search and characterise polar regions. ESA released a call for ideas for techniques, instruments techniques and experiments that could be accommodated on a lunar cargo lander launched with an Ariane 5 and deploying 1 ton of equipment in support of future human lunar exploration. In April 2009, ESA received 194 proposals to this call showing a large interest from the community.
Many thanks to Bernard for allowing us to repost his thoughtful comments. And, of course: Godspeed, LRO and LCROSS!