The red planet shows signs of rain, river deltas and canyons

Sep 27, 2008 11:17 GMT  ·  By

It is clear that once there was plenty of water on Mars. The recent findings of NASA's Phoenix Lander indicated that currently, the red planet is pretty much covered by an underground layer of water ice (non-carbonic). However, it remains to be seen exactly to what extent the Martian ice spreads. But what form did water get on Mars and when? Researchers constantly come up with newer hypotheses, relying on the discoveries of the Martian mission probes, more specifically the analysis of their pictures and soil samples.

It rained on Mars

So, where did all this water come from? Close observations of Mars' surface indicate that a huge river once crossed it and that it wasn't the only one. As scientists claim, the landscape has experienced massive rainfall. Three times, the probes that got close to the red planet photographed remains of fan-like deltas within its old craters. Ernst Hauber, a prominent geologist from the DLR (the German space agency) Institute of Planetary Research in Berlin-Adlershof explains: "We can see layered sediments where these valleys open into impact craters. The shape of certain sediments is typical for deltas formed in standing water."

  Typically, the rivers flow downstream up to a point where their currents become too weak and the sediments that they carry deposit on the bottom. NASA's Mars Global Surveyor, the European Mars Express, and NASA's Mars Reconnaissance Orbiter provided photographs that helped Hauber and fellow researchers gather data on probable valleys formed by ancient rivers that furrowed the Xanthe Terra highlands. The number of craters in the area provided clues related to the age of the planet's zonal surface. The scientists determined that waters were present in the valleys about 3.8 to 4 billion years ago, while another study showed that the sedimentation process lasted for several hundred thousand years.

  Currently, opinions on whether groundwater or rains and snowmelts had more influence on creating the valleys are still divided, and the dispute is ongoing. But the latest discoveries presented at the European Planetary Science Congress in Muenster, Germany tend to give more credit to the latter. "Our findings also point in this direction and we are convinced that both processes have played an important role in Xanthe Terra," reveals Hauber.  

When was Mars a watery place?

Common belief places the liquid-form Martian water in the Noachian Epoch, the first era of the red planet, which spanned over its first billion years, from approximately 4.6 billion years until 3.5 billion years ago. But now, the clearer pictures provided by NASA's Mars Reconnaissance Orbiter push this period up to a billion years later. The team of specialists who analyzed them found characteristics of water carving that are believed to date from the Hesperian Epoch, 3.7 billion to 3 billion years ago. The traits were discovered by Catherine Weitz, senior scientist at the Planetary Science Institute in Tucson, Arizona, and her colleagues, along the plains close to the Valles Marineris, the long canyon system from the planet's equator.

  In a press release that followed the finding, Weitz stated that "This was a big surprise, because no one thought we'd be seeing these extensive fluvial systems in the plains all around Valles Marineris that were formed during the Hesperian Era. Everyone thought that by then the climate had pretty much dried out."  

What's left of its water?  

The hundreds of tiny fractures in the red planet's surface close to its equator are thought to have behaved as a natural underground plumbing system that had channeled the waters back then. Similar formations are also found on Earth (deformation bands), caused by the groundwater's impact on the bedrock lying underground. They have a major influence on the way the groundwater circulates on Earth and there are enough reasons to believe that they had the same role on Mars as well. "Groundwater often flows along fractures such as these, and knowing that these are deformation bands helps us understand how the underground plumbing may have worked within these layered deposits," explains Chris Okubo, a geologist from the US Geological Survey in Flagstaff, Arizona, who was involved in the study of the fractures.  

Water has also changed the texture and the color of the sandstone in the regions where it was present, as seen from NASA's Mars Reconnaissance Orbiter (MRO). Suzanne Smrekar, a deputy project scientist for MRO at NASA's Jet Propulsion Laboratory in Pasadena, California, states in this regard: "This study provides a picture of not just surface water erosion, but true groundwater effects widely distributed over the planet. Groundwater movement has important implications for how the temperature and chemistry of the crust have changed over time, which in turn affects the potential for habitats for past life."

  Okubo and his team compared the fractures found on Mars with the patterns they discovered in the sandstones on Earth, in Utah, which are only a few yards (several meters) wide and several miles long. This kind of cracks are revealed when the covering rock layers erode in time. The identical fractures on Mars are lying in a 43-mile-wide (70-km-wide) crater located a bit to the north of Mars' equator named after the late astronomer Charles Capen. As Okubo and his fellow researchers stated in their study, "These structures are important sites for future exploration and investigations into the geological history of water and water-related processes on Mars."  

Another leftover, the water ice found on Mars is believed to be a promising start as a proper environment for organic life forms. Probes sent to Mars are working at full capacity in order to determine as much as possible whether or not this statement is true. The University of Arizona is the first public institution of its kind to lead a mission on the red planet. The Phoenix Mars Mission, which was scheduled to run for three months – from May to August this year, was only the first one in NASA's "Scout Program."  

"It must be ice," stated then Phoenix Principal Investigator Peter Smith in a news briefing announcing the water ice confirmation, quoted by his University of Arizona site. "These little clumps completely disappearing over the course of a few days, that is perfect evidence that it's ice. There had been some question whether the bright material was salt. Salt can't do that." As proof for the statement stood the bits of bright material dug on June 15 and still existing as a solid the following day but which vaporized by June 19. It is obvious that the lumps of material were of water ice, because carbon-dioxide ice doesn't even last for one day as a solid.

  An icy material, darker than the one found in the first trench in the NW of the lander had been located in a second trench, NE of the landing probe. Upon being backhoed, scraped and rasped, the respective locations granted new material for analysis, probing and sampling, both surface soil and hard layer.

  Life?

  Following the discovery of water ice, scientists all over the world expect further consequent results, such as finding minerals, chemicals or traces of organic matter, indicating whether microbial life ever existed under the northern surface of Mars. It still remains to be established whether water can be found or obtained in a liquid aggregation state on Mars and also whether it can provide a proper environment for organic compounds that can form organic blocks and generate life energy. Hopefully, more consistent and relevant samples will allow scientists to get the most accurate results soon.

Photo Gallery (3 Images)

Different layers record the changes in Mars' climate
Layered deposits in Valles MarinerisMars' plumbing systems in Valles Marineris
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