Mar 07 2009

India and NASA Search for the Lost Lunar Lakes

The search for the lost lunar lakes continues into the 21st Century! This adventure, worthy of Indiana Jones, will strongly influence human expansion into the cosmos. If they are found, the lakes will be the key to lunar development and human settlement of the inner solar system during the 2015 Maslow Window. If not, hydrogen may have to be imported to support future lunar science, industry, and tourism.

Our latest search for the lost lunar lakes began in 2008 at the ISRO Satish Dhawan Space Centre in Sriharikota off the coast of Andhra Pradesh in India. Click chandrayaanliftoff.jpg.

Today, the search for the lost lunar lakes involves a beautiful international collaboration between India, NASA, and others. The Chandrayaan-1 — India’s first mission to the Moon — was launched by the ISRO on October 22, 2008 using its 4-stage PSLV rocket. The vehicle achieved lunar orbit on November 8. A week later India became only the 4th entity reach the Moon’s surface (after former Soviet Union, U.S., and European Space Agency) when its Moon Impact Probe hit near the Moon’s south pole. The MIP’s impact released debris from near the crater Shackleton that may provide clues to the presence of lunar water ice. You may remember that Shackleton is a famous name associated with the “Heroic Age” of Antarctic exploration during the early 20th Century Peary/Amundsen Maslow Window.

Happily hitching a ride on Chandrayaan-1 is NASA’s Mini-SAR, a synthetic aperature radar expected to help search “the inside of (polar) craters for water ice” (Space News, 1/26/09). According to planetary scientist Benjamin Bussey of the Mini-SAR program office at Johns Hopkins University, this is “the only way to explore such areas.”

The birth of the first Space Age stimulated serious interest in the lost lunar lakes when 3 Caltech scientists proposed in 1961 that water and other volatiles could be trapped in eternally shadowed crater floors near the Moon’s poles (K. Watson, B.C. Murray, H. Brown, J. Geophys. Res. 66, 3033 (1961)), because of the Moon’s low axial tilt (only 1.5 deg vs. Earth’s 23.5 deg). Their model indicated that lunar polar cold traps would have temperatures below 100 degrees K (- 173 deg C) and could retain ices for billions of years.

Ten years after the Apollo Moon landings, UC San Diego chemist James Arnold commented that like the lunar lakes, “an important paper by Watson, Murray, and Brown (1961) seems to have been lost.” The desiccated character of the returned Moon rocks showed that any water on the Moon probably came from elsewhere, so Arnold suggested water-rich meteors and icy comets.

In 2007, the National Research Council identified the lunar (and Mercurian) polar microenvironments as “unique in the solar system” because of their potential for illuminating “the volatile flux over the latter part of solar system history.” The NRC recognizes that “cold trapping of hydrogen-bearing volatiles does occur,” but their identity (e.g., water vs. hdrogen) and sources (e.g., comets vs. lunar outgassing) are currently unknown. However they see strong links between “lunar resource utilization, science, and human exploration.”

The first really successful searcher for the lost lunar lakes was Dr. Alan Binder, who led Lunar Prospector science in 1998. According to the NRC, LP detected a “distinct neutron albedo deficit over the poles.” This implies significant concentrations of hydrogen, possibly in the form of patchy ice, but most likely not at the immediate surface.

In an email to me on March 4, Alan commented that the LP discovered “an enhancement of up to 1700 ppm of hydrogen in the permanently shadowed craters of the north and south poles over the 50 to 100 ppm in the lower latitudes.” At this point, “the theoretical arguments favor … water ice crystal, at a very low mixing ratio of around just 1%, (but) we have no proof that the hydrogen is … not just enhanced deposits of solar wind hydrogen.”

Because of the low mixing ratio of 1%, Dr. Binder believes that “a spacecraft radar/radio experiment will not detect the ‘water ice’,” so he points to the upcoming LCROSS repeat of his LP impact experiment. According to NASA, this year LCROSS will target a shadowed lunar polar crater with two large impactors; the resulting debris cloud will be analyzed for the presence of lunar water, hydrocarbons, and hydrated minerals. Launch is scheduled for April 24.

The search for the lost lunar lakes intensifies!

3 responses so far

3 Responses to “India and NASA Search for the Lost Lunar Lakes”

  1. […] A cycle carried into the dimension of time is a wave. Over at 21st Century Waves, Bruce takes a look at the megatrend cycles of society. We’re approaching critical junctures over the next 20 years or so where we will either create a space-faring civilization for humanity, or we will forego space for a while. The Moon is a critical step in learning how to fare in the space environment beyond the cradle that is Earth. One of the critical questions regarding our Moon is the nature of the elevated hydrogen readings found in and near the everdark craters, and India’s Chandrayaan-1 mission is investigating that very question in collaboration with the U.S.’s NASA. This week, Bruce takes us on a quest with India and NASA Search for the Lost Lunar Lakes. […]

  2. Paul Spudison 15 Mar 2009 at 11:27 am

    Bruce,

    Alan’s “low mixing ratio of 1%” is an interpretation, not an observation. That value is the average of the concentration the LP neutron spectrometer sees. But the resolution of that instrument is 45 km or greater. Thus, he cannot say whether that 1% is uniformly spread over large areas or if it’s highly concentrated into much smaller regions of much greater concentration; both distributions would produce the results seen in the neutron maps.

  3. Stewart Nozetteon 15 Mar 2009 at 8:21 pm

    Dr. Binder is mistaken regarding the utility of radar in detecting ice deposits on the Moon. Earthbased radar has been used to detect what are generally believed to be ice deposits in permanently shadowed craters at the poles of Mercury. The same mechanisms should operate at the Moon. Groundbased radar has been inconclusive in the lunar case because poor viewing geometry when compared to Mercury. This is why radar onboard Chandrayaan and LRO will provide a totally new view of the floors of the permanently shadowed regions. While the average concentrations of hydrogen inferred from the Lunar Prospector observations are as Dr. Binder cites, if the mechanism of concentration is cold trapping than the concentrations could be significantly higher in the permanently shadowed craters because of their restricted areas. This is especially true for the north polar craters which are smaller in shadowed area than those in the south, when compared with the resolution of Lunar Prospector hydrogen measurements. If the hydrogen measured at the north pole is cold trapped water Mercury like radar features might be detected at the north pole by Chandrayaan and LRO.

    S. Nozette
    LRO Mini RF PI

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