If there is life on Mars, we will find it here

The latest data collected by researchers shows that the crater through which Perseverance has been traveling for two years was once filled with water, and various layers of sediment have accumulated at its bottom. Later, the lake shrank and sediment brought by the river that fed it formed a vast delta. As the lake eroded over time, sediments on the crater floor were eroded away, creating the geological features visible today on the surface.

for billions of years

Radar data indicate that the period of sediment deposition and erosion occurred over billions of years, with many environmental changes occurring over the eons, so if there was ever life there, its footprints would have been left imprinted on one of the sedimentary layers.

“From orbit – we can see many different deposits, but we can’t say with certainty whether what we are seeing is their original state or whether it is a result of a long geological history,” explains David Paige, first author of the article. the result is. “To understand how these things formed, we need to know what’s beneath the surface.”

And that’s exactly what the rover has been doing since 2021. The size of a car, Perseverance is equipped with seven scientific instruments, and with them it is studying the crater’s geology and characteristics, and also collecting soil samples. Future missions will bring them to Earth so they can be studied in the best laboratories.

Between May and December 2022, Perseverance, which has advanced about 50 km in total, moved from beneath the crater toward the delta, a vast expanse of 3 billion-year-old sediment that, from space, looks very similar to River deltas are visible on Earth.

As it moved toward it, the Radar Imager for Mars Subsurface Experiment, or RIMFAX, instrument fired radar waves into the subsurface at 10-centimeter intervals and captured waves reflected from a depth of about 20 meters below the surface. Measured. Thanks to this, scientists have been able to ‘see’ the base of those sediments and reveal the ancient crater floor, now buried.

Years of research with ground-penetrating radar and RIMFAX tests on Earth had already taught researchers how to read the composition and structure of subsurface layers from their radar reflections. The resulting subsurface image shows layers of rock that can be interpreted as road cuts. “Some geologists,” Page jokes, “say radar’s ability to see beneath the surface is deceiving.”

two different periods

RIMFAX images revealed two distinct periods of sediment deposition as well as two periods of erosion. According to the study, the crater floor beneath the delta is not uniformly flat, suggesting that a period of erosion occurred before the deposition of sediments in the lake. The radar images also show that the sediments are regular and horizontal, just as they are deposited in lakes on Earth. The existence of lacustrine sediments had already been indicated in previous studies, but has now been confirmed.

“The changes we see in the rock record are driven by large-scale changes in the Martian atmosphere,” Paige explains. “It’s great that we can see so much evidence of change in such a small geographic area, allowing us to extend our findings to the scale of the entire crater.”

Together, these findings reinforce the hope that soil samples collected by Perseverance will finally contain long-awaited traces of life.