By Allison Kubo Hutchison
|Elevation map of the Jezero Crater, landing site of the Perseverance Rover. NASA/Tim Goudge|
Located on the Northwest side of Isidis Basin, Jezero Crater’s lay undisturbed except for dust storms and meteorite impacts for countless eons. Jezero Crater is an uneven half-circle where the Northeast side is worn away. There are countless craters like it on Mars, yet Jezero was selected over 30 other candidates as the new playground for NASA’s Perseverance Rover. In the future, it may become the most studied site on Mars when the samples from Perseverance are returned to Earth in a future sample return mission scheduled to launch in 2026 and return to Earth in the early Thirties.
What makes Jezero Crater so special? Currently, there is very little liquid water on Mars but in the past, billions of years ago, Mars’ climate and atmosphere could sustain liquid water. Jezero Crater was once a large stately lake. Although the water is gone, today we can detect traces of it in the rocks and minerals on the floor of the crater. Jezero Crater hosts many clays (technical term: phyllosilicates) which are produced by water eroding other rocks. Ancient rivers’ channels bisect the circular walls of the crater and brought water and more importantly sediment to the lake. The deltas formed by the river inlet are at the center of the Perseverance mission. The delta which drew from a large watershed represents a concentrated snapshot of the surrounding area.
|Colored image from NASA’s Mars Reconnaissance Orbiter Imaging Spectrometer for Mars and the Context Camera used by scientists to untangle the mineralogy of the area. NASA / JPL-Caltech / MSSS / JHU-APL|
Furthermore, careful study of the mineralogy of the source area of the deltas reveals two periods with active wet surface conditions. First, a period to produce the clay minerals and subsequently a period of overland flow to transport them to the crater lake at Jezero. Based on the sediment accumulation rates in lakes on earth, Jezero Crater may have been active for between 1 and 10 million years. A long time for a lake but an eyeblink in geologic time.
Although a long time has passed since water lapped at the lakeshore, scientists are hopeful that a signal of microbial life was preserved. Smectite, an iron and magnesium-rich group of clay minerals, was found in abundance at the delta landing site. Smectite is known for its ability to trap organic matter within the thin gap layers of its chemical structure. Organic material binds to the iron and aluminum hydroxides in the clay and could be protected from the harsh radiation, temperatures, and low pressures of the Martian surface. The presence of two periods of wet conditions adds additional hopes of recording a trace of life.
The Perseverance rover will explore the area and probe the ancient lake bed for signs of life. In addition, it will test whether it is possible to produce pure oxygen from the dominantly CO2 Martian atmosphere to demonstrate the technology could be used for a manned Mars mission. The rover will also characterize the Martian atmosphere like its sibling Curiosity and characterize Martian dust.