Iceland is the same surroundings to historic Mars

Mars is often referred to as “Earth’s twin” because of the similarities between the two planets. In fact, Mars is the second most habitable planet in the solar system after Earth. However, ongoing studies have shown that our two planets had more in common at one time. In fact, a recent study found that Gale Crater was exposed to conditions similar to Iceland today.

The Curiosity Rover has been exploring Gale Crater since 2012 in search of clues as to what conditions were like there about 3 billion years ago (when Mars was warmer and wetter). After comparing the evidence gathered by Curiosity with locations on earth, a team at Rice University concluded that Iceland’s basalt terrain and cool temperatures are the closest to ancient Mars.

The study was led by postdoctoral fellow Michael Thorpe, a Mars Sample Return Scientist at NASA’s Johnson Space Center (JSC). He was joined by Prof. Kirsten Siebach from Rice University (and member of the science and operations team for Mars the Perseverance and the Curiosity Rover), Prof. Joel Hurowitz, Associate Professor of Geology at Stony Brook University and Research Associate at Jet Propulsion NASA Laboratory.

Curiosity image showing sedimentary rocks at Gale Crater, which was likely formed more than 3 billion years ago. Photo credit: NASA

For their study, the team examined data that Curiosity had collected since landing in Gale Crater in 2012, which provides insights into the chemical and physical states of sedimentary deposits that have formed in the presence of water. By comparing the chemistry of these mudstone samples with similar formations on Earth, they were able to reconstruct what the conditions were like in front of the crater where the sediment erosion occurred.

Although the crater is known to once contained a standing lake, the climatic conditions that led to its formation are still the subject of scientific debate. While some theorize that Mars was warm and wet about 3 billion years ago (and rivers and lakes were common), others think that it was cold and dry and that glaciers and snow were common.

After reviewing the evidence, Thorpe and his team found that temperature played the largest role in the formation of mudstone from sediments deposited by ancient streams and weathered by the climate. As Thorpe stated in a Rice University press release:

“Instead, sedimentary rocks in Gale Crater describe a climate that is likely to lie between these two scenarios. The old climate was likely cold, but it also appears to have sustained liquid water in lakes for extended periods of time.

“On earth, the sedimentary rock record matures fantastically with the help of chemical weathering over time. However, on Mars, we see very young minerals in the mudstones that are older than any sedimentary rocks on Earth, suggesting that weathering was limited. “

Artist’s impression of what the “lake” at Gale Crater on Mars might have looked like millions of years ago. Credit and Copyright: Kevin Gill

For comparison, the team conducted direct studies of basalt formations in Iceland and Idaho, and consulted studies of similar sediments from different climates around the world – from Antarctica to Hawaii – that are known to vary significantly in conditions. They then performed a comparative analysis using the standard geological tool known as the chemical index of change (CIA).

This method enables geologists to infer past climatic conditions from the chemical and physical weathering of a sample. In the end, they found Iceland’s basalt terrain and cool weather best suited to the bottom of Gale Crater and Mount Sharp. The similarity between formations on Mars over 3 billion years old and sediments found in Icelandic today in rivers and lakes actually came as a surprise to the team.

In fact, the similarity is only possible because rocks on Mars have seen so little weathering (and are therefore so well preserved) for 3 billion years. Siebach, who will act as operator of the Perseverance rover after touchdown in February:

“In this study, the earth provided us with an excellent laboratory in which we could examine the effects of various climate variables on weathering at different locations. The average annual temperature had the greatest impact on the rock types in Gale Crater. The climatic zones on earth allowed us to calibrate our thermometer to measure the temperature on ancient Mars. “

“When water flows through rocks to erode and weather them, it dissolves the most soluble chemical components of the minerals that make up the rocks. On Mars we have seen that only a small fraction of the elements that dissolve most rapidly are lost from the mud compared to volcanic rocks, even though the mud is the smallest grain size and usually the most weathered. “

A river-fed sediment plain in Iceland is similar to what could have fed the Mars storm crater more than 3 billion years ago. Photo credit: Michael Thorpe

These results limit the average annual temperature change on Mars when Gale Crater was still home to a lake. Had it been warmer, more water-soluble elements in the sediment deposits would have been washed away. This is in stark contrast to today’s conditions at Gale Crater, where Curiosity recorded temperatures of 90 to 0 ° C (130 to 32 ° F) over a Martian year (687 Earth days).

The results also show that the climate has changed over time as river processes (flowing water) continued to deposit sediment in the crater – from Antarctic conditions to more Icelandic conditions. While this study focused on mudstone deposits in the lowest and oldest parts of the crater, other studies looking at other areas have shown similar results.

In short, all of these studies indicate that the Martian climate likely fluctuated and became drier over time. In parallel, according to Siebach, climate change (especially in Iceland) could shift to where the best places on earth are to study past and present conditions on Mars:

“This study offers a way of interpreting this trend more quantitatively compared to climates and environments that we know well on Earth today. Similar techniques could be used by Perseverance to understand the ancient climate around the landing site at Jezero Crater. “

Orbital image of the Jezero crater with its fossil river delta. Photo credit: NASA / JPL / JHUAPL / MSSS / BROWN UNIVERSITY

This research was made possible by support from NASA’s Solar System Workings program, which awarded Thorpe a postdoctoral fellowship from NASA, and the David E. King Field Work Award from Stony Brook University. The study “Source to Sink Terrestrial Analogs for the Paleoenvironment of Gale Crater, Mars” was recently published in JGR Planets, a journal of the American Geological Union (AGU).

Further reading: Rice University, JGR Planets

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