While NASA's Curiosity Rover has been stealing the headlines, new evidence from another of the space agency's Mars missions has revealed what appears to be a wet underground environment on the planet.
The new information comes from the Mars Reconnaissance Orbiter. It has been analyzing the Martian surface from high above the planet. One of its targets has been the floor of McLaughlin Crater, a large crater measuring 92 kilometers across and more than 2.2 kilometers deep. Scientists say the crater's depth appears to have allowed underground water, which otherwise would have stayed hidden, to flow into its center.
"A number of studies have shown rocks exhumed from the subsurface by meteor impact were altered early in Martian history, most likely by hydrothermal fluids," said Joseph Michalski from the Planetary Science Institute, and a lead author of the research. “These fluids trapped in the subsurface could have periodically breached the surface in deep basins such as McLaughlin Crater, possibly carrying clues to subsurface habitability."
The researchers say they have been able to identify carbonate and clay minerals in the layered, flat rocks at the bottom of the crater. These usually only form in the presence of water. They say there is no evidence of any large inflow channels into the crater, suggesting instead there may have been a groundwater-fed lake at its bottom.
"Taken together, the observations in McLaughlin Crater provide the best evidence for carbonate forming within a lake environment instead of being washed into a crater from outside," said Michalski.
Launched in 2005, the Mars Reconnaissance Orbiter and its six instruments have provided more high-resolution data about the Red Planet than all other Mars orbiters combined. Other Mars missions have shown that water flowed across the surface of the planet, but it remains unclear whether water was ever around long enough to provide a habitat for life.
NASA scientists are also making last minute preparations for the first drilling by Curiosity rover. The craft has been on Mars since August last year. Until now the rover has been doing little more than running systems checks and getting the lay of the land. Now though, in a depression named Yellowknife Bay the scientists plan to bring out one of its prize tools – the hammer drill.
“It's the first time we are doing this on another plant, we are going to jack hammer into rocks and then take the power we create and feed them to the rover,” said NASA Project Scientist Ashwin Vasavada.
Curiosity rover has two miniature laboratories on board. By dropping drill samples into them, they can analyze the rock's composition.
"When you analyze this powder you will find out in which conditions this power was solidified inside this rocks. Was it wet? Did it contain organic compounds? By organic we mean compounds that contain carbon. And what has been the evolution of this chemistry? The evolution of this condition, of wet conditions as we expect it was in the past around that time several billion years ago," said Francisco Diego from the Department of Physics and Astronomy at the University College London.
It is hoped the samples of Martian bedrock, along with the data collected from the Orbiter, will give scientists a broader view of the forces that shape planets.
"It does offer some insights into the evolution of the whole solar system. It's just possible that it's a place that still has life perhaps deep beneath its surface, so for all those reasons its remained a really interesting target for scientists," said the Royal Astronomical Society's Robert Massey.