In a previous post, I discussed the Mars Global Surveyor (MGS). It has returned vast amounts of data over the several years it has been orbiting Mars, but unfortunately seems to have finally stopped functioning. In that post, I mentioned that MGS had taken photographs of gullies that were thought to have been created by liquid water flowing on the surface—in some cases, the gullies seemed to have formed rather recently, but it was uncertain how recently the water may have flowed. The MGS team looked for evidence of change from previous photographs. In a press release today, they write
In June 2000, we reported the discovery, using the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC), of very youthful-appearing gullies found on slopes at middle and high latitudes on Mars. Many examples were presented in our captioned web releases and in a paper published in the journal, Science. Since that time, tens of thousands of gullies have been imaged by all of the Mars orbiting spacecraft: Mars Global Surveyor, Mars Odyssey, Mars Express, and Mars Reconnaissance Orbiter.
During the years since the original June 2000 report, the MGS MOC was used to test the hypothesis that the gullies may be so young that some of them could still be active today. The way the test was conducted was very simple: re-image gullies previously seen by MOC and see if anything changed.
In two cases, something changed.
The reports will be published in this Friday’s Science. This news is exciting for a number of reasons. One, subterranean liquid water sources could be of considerable use to future Martian colonists and explorers (if indeed such a word as subterranean may be used to describe locations below the surface of Mars). Also, this significantly increases the probability that life could be found on Mars. The planet was probably warm and wet several billion years ago, and though the atmosphere is too thin and Mars is too cold for liquid water at its surface today—there does appear to be water ice at the poles—life could have persisted or developed in underground deposits.
Though liquid water seems the likely explanation, there are possible mechanisms for this change, and it is prudent to remain skeptical. We may expect additional investigation from the newly arrived Mars Reconnaissance Orbiter with its high-resolution camera, and NASA is planning to launch the Phoenix spacecraft next year. It will land on Mars the following year, intensifying the study of our neighbor planet.