Mars is usually mentioned as “Earth’s Twin” due to the similarities the 2 planets have. In fact, Mars is ranked because the second most-habitable planet within the system behind Earth. And yet, ongoing studies have revealed that at just one occasion, our two planets had even more in common. In fact, a recent study showed that at just one occasion, the Gale Crater experienced conditions almost like what Iceland experiences today.
Since 2012, the Curiosity rover has been exploring the Gale Crater in search of clues on what conditions were like there roughly 3 billion years ago (when Mars was warmer and wetter). After comparing evidence gathered by Curiosity to locations on Earth, a team from Rice University concluded that Iceland’s basaltic terrain and funky temperatures are the closest analog terrain to ancient Mars there’s.
The study was led by postdoctoral alumnus Michael Thorpe, a Mars Sample Return Scientist with NASA’s Johnson Space Center (JSC). He was joined by Prof. Kirsten Siebach of Rice University (and member of the Science and Operations Teams for Mars the Perseverance and therefore the Curiosity rovers) Prof. Joel Hurowitz a professor geology at Stony Brook University and a search Scientist at NASA’s reaction propulsion Laboratory.
For their study, the team examined data collected by Curiosity since it landed within the Gale Crater in 2012, which provides insight into the chemical and physical states of sedimentary deposits that formed within the presence of water. By comparing the chemistry of those mudstone samples to similar formations on Earth, they were ready to reconstruct what conditions were like upstream of the crater, where the sediment erosion happened.
While it’s well-established that the crater once contained a standing lake, the climate conditions that led to its formation remains the topic of scholarly debate. Whereas some theorize that Mars was warm and wet roughly 3 billion years ago (and rivers and lakes were common) others think that it had been cold and dry which glaciers and snow were common.
After examining the evidence, Thorpe and his team determined that temperature played the most important role in how mudstone was formed from sediment deposited by ancient streams and weathered by the climate. As Thorpe explained during a Rice University press release:
Sedimentary rocks in Gale Crater falls in between these two scenarios detail a climate. the traditional climate was likely frigid but also appears to possess supported liquid water in lakes for extended periods of your time.
For comparison, the team conducted direct studies of basaltic formations found in Iceland and Idaho, and consulted studies of comparable sediments from a variety of climates round the world starting from Antarctica to Hawaii where conditions are known to change considerably. They then made a comparative analysis using the quality geological tool referred to as the chemical index of alteration (CIA).
This method allows geologists to conclude the reasons past climate conditions from chemical and physical weathering of a sample. within the end, they determined that Iceland’s basaltic terrain and funky weather were the simplest match for the ground of the Gale Crater and Mount Sharp. The similarity between development that over three billion years old on Mars and sediments found in rivers and lakes in Icelandic today was actually surprising to the team.
In effect, the similarity is merely possible because rocks on Mars have experienced so little weathering since 3 billion years ago (and are therefore so well preserved). Said Siebach, who are going to be an operator for the Perseverance rover after it touches down in February:
Earth provided a superb laboratory for us during this study, where we could use a variety of locations to ascertain the consequences of various climate variables on weathering, and average annual temperature had the strongest effect for the kinds of rocks in Gale Crater. For measuring the temperature on ancient Mars the climates on Earth let us to calibrate our thermometer.
As water flows through rocks to erode and weather them, it dissolves the foremost soluble chemical components of the minerals that form the rocks. On Mars, we saw that only a little fraction of the weather that dissolve the fastest had been lost from the mud relative to volcanic rocks, albeit the mud has the littlest grain size and is typically the foremost weathered.
These results place limits on the typical annual natural process on Mars when the Gale Crater was still home to a lake. Had it been warmer, more of the water-soluble elements within the sedimentary deposits would are flushed away. This stands in stark contrast to conditions within the Gale Crater today, where Curiosity has recorded temperatures that went from ?90 to 0 °C (?130 to 32 °F) within the course of a Martian year (687 Earth days).
The results also indicate that the climate shifted over time as fluvial processes (flowing water) continued to deposit sediments within the crater – going from Antarctic-like conditions to more Icelandic conditions. While this study focused on mudstone deposits within the lowest and most ancient a part of the crater, other studies that have looked into other areas have shown similar results.
In short, all of those studies indicate that the Martian climate probably fluctuated and have become drier with time. In parallel, says Siebach, global climate change (especially in Iceland), may shift where the simplest places on Earth for studying past and present conditions on Mars are located:
This study establishes a method to interpret that trend more quantitatively, by comparison to climates and environments we all know well on Earth today. Similar techniques might be employed by Perseverance to know ancient climate around its landing site at Jezero Crater.
This research was made possible because of support provided the NASA system Workings program which issued a NASA postdoctoral fellowship to Thorpe and David E. King Field Work Award. The study, “Source?to?Sink Terrestrial Analogs for the Paleoenvironment of Gale Crater, Mars,” recently appeared in JGR Planets.