Ancient Mars Had Warm Weather and Rainstorms Before the Planet Turned Icy, Scientists Say - Newsweek

The climate on Mars between 3 and 4 billion years ago may have been warm enough to sustain significant rainstorms and flowing water before conditions turned cold and the planet froze over, according to research.

The existence of ancient valley networks and lake deposits on the red planet indicate that liquid water was once abundant on the surface. However, scientists have not been able to agree on whether the climate was warm and wet, or cold and icy

But now, findings presented at the Goldschmidt Geochemistry Conference in Barcelona on Monday by Briony Horgan have cast new light on Mars' ancient climate, indicating that the Red Planet had one or more long periods were dominated by rainstorms and flowing water, before the surface water froze.

"We know there were periods when the surface of Mars was frozen; we know there were periods when water flowed freely," Horgan said in a statement. "But we don't know exactly when these periods were, and how long they lasted."

To understand more about the planet's ancient climate, Horgan and her colleagues compared data on patterns of Martian mineral deposits—collected by NASA spacecraft and rovers—with similar information on regions of Earth considered to be analogs of Mars.

"We have never sent unmanned missions to areas of Mars which can show us the earliest rocks, so we need to use Earth-bound science to understand the geochemistry of what may have happened there," Horgan said. "Our study of weathering in radically different climate conditions such as the Oregon Cascades, Hawaii, Iceland, and other places on Earth, can show us how climate affects patterns of mineral deposition, like we see on Mars."

"Here on Earth, we find silica deposition in glaciers which are characteristic of melting water," she said. "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 three to four billion years ago, we had a general slow trend from warm to cold, with periods of thawing and freezing."

However, while these findings support the idea of this slow warming trend, climate models of ancient Mars struggle to produce scenarios where surface water could have remained unfrozen. This is because the planet received only a limited amount of heat from sunlight. This means scientists may have overlooked certain chemical, geological or other factors, which may have contributed to warming earlier in the planet's history.

Warmer conditions increase the possibility that life developed on early Mars, the researchers say. Thus the latest results could have significant implications in the search for life there.

"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."

Scott McLennan, a professor from Stony Brook University New York who was not involved in the research, praised Horgan's study.

"What is especially exciting about this work is that it used well-understood Earth-based geological processes from regions that are good analogs for Mars," he said. "The results not only make sense from the perspective of developing climate evolution models for Mars but also demonstrated a possible mechanism for forming the most interesting and perplexing and non-crystalline components that have been found in all of the samples analyzed so far by the Curiosity rover."