Nasa’s Perseverance rover sends back images of Martian river delta
Image credit: nasa
Nasa’s Perseverance rover has sent back its first images of a 3.7-billion-year-old ancient river delta that reveal a complex picture of the planet’s now-dried-up water cycle.
The pictures also provide insight into where the rover could best hunt for samples, including those that may contain signs of past life, known as biosignatures.
Billions of years ago, when Mars had an atmosphere thick enough to support water flowing across its surface, river flows carried sand and gravel from the surrounding highlands towards Jezero’s fan-shaped river delta.
The lake in the crater – Lake Jezero – could have been up to 40km wide and tens of metres deep, researchers believe. They hope the findings could help Perseverance achieve its scientific missions of finding signs of former life and collecting samples for future return to Earth.
Soon after landing in February this year, the rover’s Mastcam-Z cameras and Remote Micro-Imager (RMI) zoomed in for a closer look at one of the crater’s most massive geological features, the ‘Delta Scarp’.
The scarp contains the remnants of a river delta that formed where a 120-mile-long ancient river and a 21-mile-wide lake join.
The Perseverance science team detected a prominent hill, which they called Kodiak, near the scarp and discovered it contained distinctive geological structures. Within its cliff face, they observed metres of sloping rock beds sandwiched between horizontal layers that indicate rocky deposits from the ancient delta.
The teams believes this confirms the presence of the delta that built into a lake in Jezero crater and suggests that there was steady water flow into the lake, which is consistent with a warm and humid Martian climate 3.7 billion years ago.
Co-lead author on the paper professor Sanjeev Gupta, of Imperial College London’s Department of Earth Science and Engineering, said: “These results have an impact on the strategy for the selection of rocks for sampling. The finest grained material at the bottom of the delta probably contains our best bet for finding evidence of organics and biosignatures, and the boulders at the top will enable us to sample old pieces of crustal rocks.
“Both are main objectives for sampling and caching rocks before the Mars Sample Return – a future mission to bring these samples back to Earth.”
Perseverance collected its first sample of Martian rock from the planet’s surface in September, although it is not expected to be delivered back to Earth for many years.
Early in Lake Jezero’s history, it was thought to be tens of metres deep, with water levels reaching high enough to break through the eastern crater rim, where images taken from orbit show an outflow event occurred.
The lake is thought to have fluctuated greatly over time, with its depth rising and falling by tens of metres before eventually disappearing altogether.
While it is unknown if these swings in the water level were a result of flooding or more gradual environmental changes, the team determined that they occurred during a time later in the history of the Jezero delta when lake levels were at least 100 metres lower.
Professor Gupta said: “A better understanding of Jezero’s delta is a key to understanding the change in hydrology for the area, and it could potentially provide valuable insights into why the entire planet dried out.”
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