The results are now in from the first sample of Mars regolith to be baked in Phoenix’s oven. It’s not good news… there’s no water. After a difficult time of actually delivering the sample to the Thermal and Evolved Gas Analyzer (TEGA) – a.k.a. the “oven” – scientists were hopeful for a clear science run. They were finally able to sift the clumpy regolith through the TEGA screen last week. However, the sample was waiting on the deck of Phoenix for some time until tests could be carried out on the sample; it seems probable that any water ice will have sublimed into the thin atmosphere. This first null result by no means suggests the area is devoid of water, Phoenix has many more water-finding tricks up its sleeves yet…
On June 11th, Phoenix mission control breathed a sigh of relief as they found a solution to the problem of getting the clumpy Mars regolith through the oven screen. Over the weekend they were able to carry out the first tests on the sample and it appears that everything functioned as it should when the sample was heated to 35°C (95°F). At this temperature any water in the sample will have melted. In the second phase of the test, the sample was heated up to 175°C (350°F). No water vapour was detected.
“We saw no water coming off the soil whatsoever” – William Boynton, TEGA team leader, University of Arizona.
Scientists are in no way surprised or discouraged about this early result. The regolith sample sat atop the lander’s TEGA hatch for several days whilst scientists tried to find an answer as to why no particles had fallen into the oven. It is believed that any water ice in the sample will have quickly vaporized in the Martian sunlight and thin atmosphere. As the atmospheric pressure is so low on Mars, exposed water ice cannot melt into liquid water, it will sublime straight to water vapour (by-passing the liquid phase).
Over the coming days, scientists will instruct Phoenix to fire up the TEGA again to heat the sample to 1000°C (1800°F). This will vaporize minerals that might be chemically bound to H2O, CO2 or SO2 and then use instrumentation to measure the vented gases. Scientists are very confident that, although water has not been directly detected today, they will detect evidence of its existence in the next round of tests.
Whilst the drama unfolds in the lander’s oven, Phoenix continues its excavation work on the surface with its robotic arm. It has just expanded a trench (a 3D visualization can be seen at the top of this post) by linking the two trenches “Dodo” and “BabyBear” into a new united “Dodo-Goldilocks” trench. This is the location where scientists noticed white sediment last Friday, so they will be keen to learn whether this is water or salt.