Life may have existed on warm, rainy, ancient Mars before winter came

The knowledge of water on ancient Mars has been common for years, but its form was up for debate. Scientists were unsure whether the water was trapped in ice or it actually flowed over the surface. There was also uncertainty over the duration of flowing water if temperatures were warm enough to allow it.

A warm surface with flowing water supports the idea that life could have formed independently on the planet's surface.

The new study includes a comparison of mineral deposit patterns with those on Earth, which paints a picture of one or perhaps even several long-term periods of a warm Mars with rainstorms and flowing water. Later on, as temperatures dropped, the water would freeze.

Today, the average temperature on Mars is negative 80 degrees Fahrenheit. Between that and the thin atmosphere, Mars has a harsh environment when compared with its warmer past.

"Here on Earth, we find silica deposition in glaciers which are characteristic of melting water," said Briony Horgan, a professor at Purdue University. "On Mars, we can identify similar silica deposits in younger areas, but we can also see older areas which are similar to deep soils from warm climates on Earth. This leads us to believe that on Mars 3 to 4 billion years ago, we had a general slow trend from warm to cold, with periods of thawing and freezing. If this is so, it is important in the search for possible life on Mars."

Horgan presented the paper at the Goldschmidt Geochemistry Conference this week in Barcelona.

Comparing the mineral deposits could shed light on the similarities between ancient Mars and ancient Earth, something that missions to Mars could investigate.

On Earth, climate affects the patterns of how minerals are deposited. The same pattern was observed on Mars.

"We know that the building blocks of life on Earth developed very soon after the Earth's formation, and that flowing water is essential for life's development," Horgan said. "So evidence that we had early, flowing water on Mars, will increase the chances that simple life may have developed at around the same time as it did on Earth. We hope that the Mars 2020 mission will be able to look more closely at these minerals, and begin to answer exactly what conditions existed when Mars was still young".

There are no unmanned missions investigating the oldest rocks on Mars. The data for the study was gathered by NASA's Compact Reconnaissance Imaging Spectrometer for Mars.

"If our findings are correct, then we need to keep working on the Mars climate models, possibly to include some chemical or geological, or other process which might have warmed the young planet," Horgan said.