June 21, 2008

Phoenix Finds Water on Mars

Finally, water ice has been found on the martian surface. The Phoenix Mars lander took a scoop of regolith on Sol 20 (June 19th), exposing a white powdery substance. Immediately, scientists announced that the substance was either some form of ice or salt deposits. The prime mission objective for Phoenix is to look for evidence for water, past and present, in the uppermost layers of the surface. Although tests on excavated material are ongoing inside the onboard oven instrument (the Thermal and Evolved Gas Analyzer, or TEGA), baking the sample and analysing the vapour produced, Phoenix scientists have discovered water ice simply by taking two photographs four sols apart. This discovery will naturally boost hopes that water could be harvested from the top layers of martian regolith by future Mars colonists.

"It is with great pride and lot of joy that announce today we have found the proof that we have been seeking that show that this hard, white material is water ice." - Phoenix principle investigator Peter Smith.

But how are the team sure they are looking at water ice? by taking two images of the trench dug by Phoenix's robotic arm, they were able to measure the quantity of the white substance uncovered in the top of the suspected permafrost layer of Mars. By taking a second picture of the area four Mars-days (or Sols) later, they noticed a marked decrease in the amount of the white deposit. If the deposit was from a mineral or salt, there would be no difference in the quantity measured. If the deposit was something like frozen carbon dioxide, when uncovered by the digger, it would have evaporated instantly (as the boiling point of CO₂ is very low). In this case there would have been no chance to image the CO₂ deposit. It would appear there has been a slower sublimation process at work, where the prime candidate (water ice) has gradually vented into the atmosphere over the four days.

"We're confident now that this is water ice. We've hit what we're looking for. The job now is to find out what is mixed in with the ice, how much salt is there, how many organics are there, and these are the things we'll need TEGA and MECA to solve." - Mark Lemmon, Co-Investigator, Phoenix Surface Stereo Imager

These are very exciting times. Although there has been strong indicators that water does exist on Mars, this is the first in-situ photographic evidence of ice crystals mixed in with the top layer of fine Mars "soil" (a.k.a. regolith - pulverized grains of rock from repeated meteorite impacts and other geological processes). Now we eagerly anticipate the results from the TEGA and MECA (Microscopy, Electrochemistry and Conductivity Analyzer) to see what compounds (organic or otherwise) are mixed in with the ice.

For more information on this historic find see:

• Nancy Atkinson's article over at the Universe Today


• Phoenix Mars Mission website

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