Many people wonder if there has ever been water on Mars. But researchers from the Department of Geological Sciences have a few more questions - What did the water contain? How long might it have been there?
Last month, department researchers presented a study of ancient lakes on Mars at the Lunar and Planetary Science Conference in The Woodlands, Texas that sought to answer some of these questions. The study, published online last month in the journal Icarus, focuses on sedimentary deposits in former Martian lake beds and may have implications for future rover missions, said the article's chief author Timothy Goudge GS.
The research group, led by Professors of Geological Sciences James Head and Jack Mustard, Goudge and post-doctoral research student Caleb Fassett, studied 226 lake beds in order to determine the existence and makeup of their sedimentary deposits - which would indicate the past presence of water - and the geological processes at work in forming them.
"The whole question is, 'What's going on in early Mars climate history?'" Head said. The debate in the scientific community, he said, is whether Mars was warm and wet or cold and dry, "like Antarctica," in the past. By looking for sedimentary deposits, the researchers hoped to get closer to answering this question.
The researchers found that roughly a third of the lake beds had sedimentary deposits. Of these, 10 had clay deposits, which are good at preserving signatures of life, such as fossils, Goudge said. These clay deposits would provide good landing spots for future rovers seeking evidence of past and present life on the planet, he said.
Additionally, the lack of interaction between lava and water indicates that any water that may have been on Mars in the past "didn't stick around for very long," Head said.
Goudge said the researchers used two main methods to study these lake beds: satellite imagery and near-infrared spectroscopy (NIRS).
The former method used pictures taken by NASA- and European Space Agency-operated satellites, such as the Mars Reconnaissance Orbiter, to determine which geological processes took place in a given spot. For example, volcanic flows are characterized by visible ridges and sedimentary deposits by a "delta" shape, Goudge said.
NIRS is used to assess the chemical makeup of deposits by analyzing the light reflected off of them, examining not only visible rays but also infrared. "Colors only tell you part of the picture," he said.
The researchers found the most common geological process in these lake beds was volcanic flow. This presented one of the major challenges of the study, as "it can be really difficult to assess the composition of the deposits" underneath volcanic flows, Goudge said.
Beyond rover missions, the study has various implications for future research. It raises questions about the presence of clay in Martian lake beds and why there is not as much of it as there is on Earth.
Goudge sees two possible scenarios - that the chemistry of water on Mars is different from that on Earth or that water was not flowing on Mars for as long as it was on Earth. Goudge and Head said future research will try to resolve which is more likely.
"We've known that craters on Mars supported lakes of water, but this study supports the notion that these wet periods were probably transient, as opposed to long-lived bodies of water," said Lee Saper '12, who has participated in past research on Mars' geology but was not involved in this study. "Besides being important in our understanding of the geologic evolution of the planet and its hydrology, this also has implications for the astrobiological relevance of crater lakes on Mars as potentially habitable locations."
Saper added that the information found in the study helps to inform the work the Mars Science Laboratory, a rover landing at Gale Crater in August, will perform in investigating lake bed mineral deposits.
