Recent studies have shown that billions of years ago, Mars was warm and wet. This finding contrasts with an alternative theory that this era was primarily cold and icy. This result has implications for the idea that life may have arisen on Earth at this time.

Whether Mars was ever habitable is an interesting topic that has been intensely studied for decades. MarsLike Earth, it is approximately 4.5 billion years old and its geological history is divided into different eras.

latest papers This concerns Mars during an era known as the Noachian Age, which lasted from about 4.1 billion to 3.7 billion years ago. This was during a phase in the history of the solar system called the “Epoch Epoch.” Late Heavy Bombing (LHB). Evidence of truly catastrophic meteorite impacts during the LHB has been found on many objects throughout the solar system.

Two obvious scars on Mars from this era are the giant Hellas impact basin and the Argyre impact basin. Both are well over a thousand miles in diameter, and each has enough volume to easily hold all the water in the Mediterranean Sea.

Although it may be hard to imagine that such an era would be an era in which fragile life forms could easily exist, it is highly likely that Mars was the most habitable era. Evidence of water-carved landforms from this period is abundant, including dry river valleys, lakebeds, ancient coastlines, and deltas.

The general Noachian climatic conditions are still hotly debated. Two alternative scenarios Common theories suggest that this period was either cold and icy, with occasional meteorite strikes or volcanic eruptions causing large amounts of frozen water to melt, or that the region was warm and humid with little ice.

shining sun

All stars, including the Sun, become brighter with age. In the early solar system, during the Noachian period, the Sun was about 30% dimmer than it is today, so less heat reached Mars (and all the planets). To maintain a warm and humid climate at this point, Mars’ atmosphere would have to be very rich, much thicker than it is today, and rich in greenhouse gases like CO2.

However, once atmospheric pressure is high enough, CO2 tends to condense out of the air. form clouds and reduce the greenhouse effect. Given these issues, the cold frozen scenario is probably more believable.

One of the main goals of science is Mars 2020 Perseverance RoverWhich landed nicely In February 2021, we will be looking for evidence to support either of these two scenarios. new paper Using Perseverance’s data, they may be able to do just that.

Perseverance landed in Jezero Crater on Mars. It was chosen as the landing site because Mars was once located there. lake. Viewing the crater from orbit, you can see several distinctive fan-shaped deposits ejected from channels carved into the crater’s walls by flowing water. There are rich deposits of clay minerals within these channels.

A new paper details a recent analysis of aluminum-rich clay pebbles called kaolinite that are present in one of the ancient channels. These pebbles appear to have undergone intense weathering and chemical alteration by water during the Noachian.

This may not be surprising in a known ancient aquatic environment, but what is interesting is that these clays are significantly depleted in iron and magnesium and enriched in titanium and aluminum.

This is important because it means these rocks are unlikely to have been altered in a hydrothermal environment, where melting ice caused by volcanic activity or meteorite impacts temporarily releases scorching hot water.

Rather, it seems to have changed due to moderate temperatures and continuous heavy rain. The authors found clear similarities in the chemical composition of these clay pebbles to similar clays found on Earth dating back to a time in Earth’s history when the climate was much warmer and wetter.

The paper concludes that these kaolinite pebbles were altered under wet conditions comparable to “Earth’s past greenhouse climate,” and “likely represent some of the wettest periods in Mars’ history, and perhaps the most habitable.”

Furthermore, the paper concludes that these conditions may have persisted over periods ranging from thousands to millions of years. Perseverance also recently made headlines for the following discovery: Possibility of biosignature Some of the samples collected last year were also taken from inside Jezero Crater.

These precious samples are now being stored in a special sealed container on the rover for collection by a future Mars sample return mission. Unfortunately, that mission has recently been cancel by NASA, so what important evidence they may or may not contain will probably not be tested in a laboratory on Earth for many years.

Important for this future analysis is the so-called “Noll criterion.” This is a concept formulated by astrobiologist Andrew Knoll that for something to be evidence of life, the observation must be explainable simply by biology. It cannot be explained without it. We will only know if these samples meet the Nord criteria if they are brought to Earth.

In any case, it’s quite impressive to imagine the days of Mars billions of years before the first humans landed on Earth. The now desolate, windswept landscape of Jezero Crater once contained a tropical climate, perhaps with a living ecosystem.

Gareth DorianSpace Science Postdoctoral Researcher, University of Birmingham

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