NASA rover confirms existence of ancient lake on Mars – DW – 01/30/2024

If life ever existed on Mars, it must have been located in the ancient Jezero Crater Lake. To test this, NASA’s Perseverance rover collected samples of lacustrine sediments (from a lake) that scientists showed could contain remnants of life.

A study published in the journal Science Advances and led by a team of scientists from the universities of California (UCLA) and Oslo (Norway) showed that at some point the crater filled with water, which deposited layers of sediment on the crater floor.

Subsequently, the lake shrank and sediment carried by the river that fed it formed a huge delta, and over time, as the lake disappeared, the sediments in the crater eroded, forming the geological features visible on the surface today.

According to the Perseverance radar, all of these periods of deposition and erosion at Jezero Crater occurred over several eons (geochronological units) of environmental change, confirming what was already seen in images of Mars taken from space.

“From orbit we see many different deposits, but we cannot say with certainty whether what we see is their original state or the end of a long geological history. To find out how they formed, we have to look below the surface,” explains David. Page from UCLA and first author of the paper.

To this end, starting in 2021, a NASA rover equipped with seven scientific instruments will explore the crater (48 kilometers wide), study its geology and atmosphere and collect soil and rock samples that will be returned to Earth by a future expedition. be analyzed for evidence of past life.

Persistence confirms existence of lake sediments

Between May and December 2022, Perseverance moved from the crater floor to a delta, a vast expanse of 3-billion-year-old sediment similar to river deltas on Earth.

As the rover moved deeper into the delta, the RIMFAX (Radar Imaging for Mars Subsurface Experiment) instrument beamed down radar waves at 10-centimeter intervals and measured the reflected pulses from about 20 meters below the surface.

In this way, scientists were able to see the base of the sediments and reveal the upper surface of the buried crater floor.

After years of ground penetrating radar research and testing RIMFAX on Earth, scientists have learned to read the structure and composition of underground layers from their radar reflections.

The image of the subsurface shows layers of rock that can be interpreted as a road cut. RIMFAX images revealed two distinct periods of sediment deposition, sandwiched between two periods of erosion.

According to UCLA and the University of Oslo, the crater floor located beneath the delta is not uniformly flat, suggesting that there was a period of erosion before the lake sediments were deposited.

The radar images show that the sediments are regular and horizontal in shape, like those deposited in lakes on Earth, and confirm the existence of lake sediments, which was suspected but not confirmed.

A second period of deposition occurred when fluctuations in lake level allowed the river to develop a wide delta that once extended into the lake but was now eroded closer to the river’s mouth.

“The changes we see in the rock record are driven by large-scale changes in the Martian environment,” explains Page. “It’s remarkable 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,” he says.

ee (EFE, Reuters)