Some billions of years ago, Mars probably had ponds and rivers which could have been a potential habitat for microbial lives. The planet changed over time and its atmosphere thinned due to the evaporation of water. However, it left behind some frozen evidence that planetary scientists have been studying for years to gather information about the history and ancient lives of the Red Planet.
The Mars Reconnaissance Orbiter (MRO) spacecraft, designed and launched by the National Aeronautics and Space Administration (NASA), has been surveying the atmosphere and geology of Mars from its orbit since 2006. In a recent research published in the journal AGU Advances, California Institute of Technology, USA, researchers used MRO data and concluded that water may have been present on the planet much longer than thought earlier.
The latest findings suggest that water left salt minerals on the surface of Mars as recently as two billion years ago. It has been believed that water on the Martian surface evaporated about three billion years ago. However, the new findings from the MRO data, research done over the last 15 years, have shed new light on water’s existence and hence the possibility of ancient lives on Mars.
The new estimates, which centered on chloride salt deposits on the planet’s surface—left behind by the evaporating water—have significantly reduced the timeline of the existence of water. The researchers studied dozens of images of the salt deposits taken by the MRO and estimated their age with the help of a technique known as crater counting. A younger region will have fewer craters with an adjustment with various other factors like the planet’s atmosphere.
The researchers used the images of the salt deposits taken by the Compact Reconnaissance Imaging Spectrometer for Mars, installed in the MRO, in the southern hemisphere of Mars, which has terrains with numerous impact craters that are one of the keys to dating the salts.
Leslie Tamppari, deputy project scientist of MRO at the jet propulsion laboratory of NASA, commented on the new findings: “Part of the value of MRO is that our view of the planet keeps getting more detailed over time. The more of the planet we map with our instruments, the better we can understand its history.”
The MRO has two cameras that are perfect for the research. The Context Camera has wide-angle lens which helped the scientists in mapping the extent of the salt deposits. The High-Resolution Imaging Science Experiment colour camera allowed them to zoom into the salt deposits. When used co-ordinately, the cameras helped the scientists to create digital elevation maps.
The researchers, Ellen Leask and Bethany Ehlmann, found that many of the salts had depressions which were home to shallow ponds. The scientists also found dry channels nearby hinting at the existence of former streams that flowed into the ponds.
“What is amazing is that after more than a decade of providing high-resolution images, stereo and infrared data, the MRO has driven new discoveries about the nature and timing of these river-connected ancient salt ponds,” commented Ehlmann, the corresponding author of the research.
The salt minerals that the study has been based upon were discovered by another NASA spacecraft Odyssey, launched in 2001. The MRO, equipped with more high-resolution instruments, was launched in 2005.