NASA's Mars Perseverance rover, equipped with ground-penetrating radar, has verified that the Jezero crater, created by an ancient meteor impact near Mars' equator, once contained a large lake and river delta.
The geological formations currently observed on the crater's surface have been shaped over time by sediment deposition and erosion. The identification of lake sediments enhances the optimism that soil and rock samples gathered by Perseverance may contain traces of ancient life.
Martian Delta Reveals Ancient Lake
The Perseverance rover, landing on Mars in February 2021 with its retired companion Ingenuity, utilized ground-penetrating radar to unveil layers of sediment from a past lake that evolved into a massive delta.
The discovery fuels optimism for finding evidence of ancient Martian life when geological samples collected by Perseverance return to Earth, with the findings published in a paper, titled "Ground penetrating radar observations of the contact between the western delta and the crater floor of Jezero crater, Mars," in Science Advances.
Lead study author David Paige from UCLA emphasized the challenge of understanding geological formations from orbit, highlighting the need to delve beneath the Martian surface for a comprehensive understanding. Perseverance, a pivotal component of NASA's $2.7 billion Mars 2020 mission, explores the 30-mile Jezero crater alongside the older Curiosity rover, actively searching for signs of ancient life through rock sample collection.
Equipped with the Radar Imager for Mars' Subsurface Experiment (RIMFAX), Perseverance employed ground-penetrating radar to create a map, revealing sediment existence, and affirming past assumptions. The crater's history indicates it was once submerged in the waters of a vast lake, with river-formed deltas undergoing deposition and weathering through distinct phases of erosion.
The recorded changes in the Martian environment within this small geographic area provide valuable insights, extending findings to the entire crater. The presence of water is a crucial indicator, given Earth's dependence on water for life, heightening the possibility of past or present Martian life.
Two Distinct Periods of Sediment Deposition in Jezero Crater
Years of utilizing ground-penetrating radar and testing RIMFAX on Earth have provided scientists with the expertise to interpret subsurface layers' structure and composition from radar reflections. The resulting subsurface image depicts rock layers comparable to a highway road cut, offering a unique insight into Mars' geological history.
RIMFAX imaging, considered by some geologists as akin to "cheating," disclosed two distinct periods of sediment deposition sandwiched between two phases of erosion.
The report from UCLA and the University of Oslo highlights that the crater floor beneath the delta is not uniformly flat, indicating a prior period of erosion preceding the deposition of lake sediments. Radar images reveal regular and horizontal sediments, mirroring those found in Earth's lakes, confirming suspicions from prior studies.
Another phase of deposition occurred when fluctuations in the lake level allowed the river to form a broad delta, extending far into the lake initially and eroding back closer to the river's mouth over time.
Lead study author David Paige emphasizes the significance of these findings, noting that the preserved changes in the rock record reflect large-scale shifts in the Martian environment.
The ability to observe substantial evidence of change in a relatively small geographic area allows researchers to extrapolate these findings to the entire crater, providing valuable insights into Mars' dynamic geological evolution.
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