In two days (Thursday, February 18, 2021) NASA’s Perseverance Rover will land on Mars. As the newest robotic mission in the Mars Exploration Program (MEP), Perseverance will follow in the footsteps of its sister mission Curiosity. Just in time for its arrival, studies at the Southwest Research Institute (SwRI) have shown that the surface of Mars was shaped by flowing water several million years earlier than previously assumed.
The mystery of how Mars went from a warmer, watery planet to an extremely cold and arid planet billions of years ago is one of the general scientific goals of the Perseverance rover (as is finding evidence of past or present lives). When the rover arrives at Jezero crater, it will examine the sediment deposits and take samples, which are the remains of the ancient river delta.
Research suggesting that these formations formed eons earlier than previously thought was carried out by Dr. Simone Marchi – a Senior Scientist in the SwRI office in Boulder, Colorado. For his study, recently published in the Astronomical Journal, Dr. Marchi used the dynamic models for the formation and evolution of the solar system to create a new chronology for Mars.
The Jezero crater on Mars is the landing site for NASA’s Mars 2020 rover. Photo credit: NASA / JPL-Caltech / ASU
Like Dr. Marchi recently stated in a press release from SwRI:
“The idea behind crater dating isn’t rocket science. The more craters, the older the surface. But the devil is in the details. Craters form when asteroids and comets hit the surface. The rate of these cosmic crashes over the eons is uncertain and hinders our ability to convert crater numbers into terrain ages. I took another look at this and built on the latest developments as we understand the earliest evolution of the solar system. “
Simply put, scientists have typically relied on measurements of the natural radioactivity of rocks to determine the ages of various areas on earth. On Mars, however, scientists have largely adhered to counting impact craters to determine the chronology of the landscape. The reason for this lies in the moon rock samples that were brought back by the Apollo astronauts.
For decades, scientists have used the radiometric ages of these rocks to create and calibrate a chronology for lunar craters, which was then used to extrapolate the ages of craters on Mars. However, this method has encountered problems when it comes to the earliest evolutionary periods of the solar system. Over the past few years, our understanding of the timing of the effects of the Moon and Mars has improved significantly.
In anticipation of Perseverance’s arrival, Dr. Marchi his analysis on the Jezero crater. This impact crater with a diameter of about 48 km is located in the Isidis Basin, which has a diameter of 1200 km and was formed by an earlier and more massive impact. Isidis could be the largest and oldest basin on Mars, cutting a large part between the Borealis Basin and the Syrtis Major Planum.
A computer simulation showing a hypothetical evolution for an early Mars that was heavily afflicted by cosmic influences. Image Credit: SwRI
The existence of smaller craters in larger (older) craters is of particular interest to scientists as samples from these areas could provide data on the timing of these sequential effects. This makes these results all the more meaningful as one of Perseverance’s primary scientific goals is to study potentially habitable environments on Mars that may still show signs of survival.
Because of this, the rover’s job is to take samples from the clay-rich terrain and river delta in the Jezero crater, which are considered evidence that the crater was once home to a lake. Like Dr. Marchi said:
“These surfaces could have formed over 3 billion years ago, up to 500 million years older than previously assumed. NASA plans to have Perseverance collect and package surface samples that can be collected by a future mission for return to Earth for radiometric dating. This could provide vital data on the basic truth to better calibrate our chronology models. “
Once the Sames are cached, they will be returned to Earth by a sample return mission provided by the European Space Agency (ESA). This mission consists of four elements: a Sample Return Lander (SRL), which will be deposited in the Jezero crater, a Sample Fetch Rover (SFR), which will retrieve it and bring it to the lander, and a Mars Ascent Vehicle (MAV) will put it in the Bring orbit and a Sample Return Orbiter (SRO) that will meet with the MAV and bring the samples home.
Therefore, it is of particular importance for scientists to have an accurate timeline for these surfaces (how and when they formed and evolved). According to the new model by Dr. Marchi, the Isidis Basin is now estimated to be 4 to 4.2 billion years old, which is an upper limit to the formation of the Jezero crater and the existence of running water in the area.
Once the Perseverance rover lands and begins scientific operations, it will deploy a range of advanced instruments to study the Martian landscape. In addition to its sample caching device, spectrometers, and drill, a small, autonomous rotary-wing aircraft (the Mars helicopter) will be deployed to demonstrate aerial technologies and their effectiveness on Mars.
The mission to rebuild Mars’ past and unravel its secrets continues and is sure to get much more exciting soon!
Further reading: SwRI, The Astronomical Journal
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