NASA’s Perseverance rover reveals ancient history of Mars’ lake.

 

Celebrating its 1,000th day on Mars, NASA’s Perseverance rover has successfully explored an ancient river delta on the Red Planet, uncovering crucial evidence of a prehistoric lake within Jezero Crater. Throughout its mission, the rover has diligently collected 23 samples, shedding light on the geological history of this Martian region. Notably, the sample named “Lefroy Bay” boasts an abundance of fine-grained silica, a substance recognized for preserving ancient fossils on Earth.

Another sample, “Otis Peak,” contains a significant quantity of phosphate, often linked to life as we understand it. Both samples are rich in carbonate, providing a record of the environmental conditions during the rock’s formation. These groundbreaking discoveries were presented at the American Geophysical Union fall meeting in San Francisco on Tuesday, December 12.

Image of Jezero Crater.

This composite image of Mars’ Jezero Crater combines the crater’s visual data with mineral information detected from orbit. The green hue signifies the presence of carbonates, minerals that typically form in aqueous environments conducive to preserving traces of ancient life. NASA’s Perseverance rover is currently exploring the green region above Jezero’s fan, guided by the choice of Jezero Crater as a landing site due to orbital evidence indicating a past lake within the crater.

A lake represents a potentially habitable environment, and delta rocks, identified through orbital imagery, offer an ideal setting for preserving ancient life signs as fossils in the geological record. Perseverance’s project scientist, Ken Farley of Caltech, highlights the comprehensive exploration that has revealed the crater’s geological history, tracing its phases from lake to river.

Jezero Crater, shaped by an asteroid impact almost 4 billion years ago, became the focus of NASA’s Perseverance mission after its landing in February 2021. The mission team’s exploration unveiled diverse geological features on the crater floor, including igneous rocks formed either from subterranean magma or volcanic activity at the surface. Subsequent discoveries include layers of sandstone and mudstone, indicating the establishment of the crater’s first river hundreds of millions of years later. Above these formations lie salt-rich mudstones, pointing to the existence of a shallow lake undergoing evaporation. The team hypothesizes that this lake eventually expanded to a remarkable width of 22 miles (35 kilometers) and a depth of up to 100 feet (30 meters).

Subsequent to early history, fast-flowing water played a significant role in shaping Jezero Crater. This water carried boulders from areas outside Jezero, depositing them on the delta and various locations within the crater. Libby Ives, a postdoctoral fellow at NASA’s Jet Propulsion Laboratory in Southern California, emphasized the importance of the close examination conducted by Perseverance in understanding the intricate timeline of Jezero’s geological evolution. While orbital images provided a broad overview of these chapters in Jezero’s history, the rover’s close-up exploration has been instrumental in gaining a detailed understanding of the timeline.

Perseverance Rover Unearths Enticing Samples on Mars.

Perseverance’s collected samples, each approximately the size of a classroom chalk piece, are securely stored in specially designed metal tubes, marking a crucial phase in the Mars Sample Return campaign. This collaborative initiative involves both NASA and the European Space Agency (ESA). Transporting these tubes back to Earth would provide scientists with the opportunity to examine the Martian samples using sophisticated laboratory equipment impractical to send to Mars. In the sample collection process, Perseverance employs an abrasion tool to expose a portion of a target rock, followed by a detailed analysis of the rock’s chemistry using precision instruments, including the JPL-built Planetary Instrument for X-ray Lithochemistry (PIXL).

During its mission, Perseverance’s sophisticated instrument, PIXL, focused on a specific target dubbed “Bills Bay.” PIXL’s analysis at this location revealed the presence of carbonates, minerals known to form in aquatic settings conducive to preserving organic molecules—a key consideration for potential signs of past life. Furthermore, the rocks in Bills Bay exhibited high concentrations of silica, a material renowned for its ability to preserve organic molecules, encompassing those associated with both geological and biological processes. These findings add valuable insights into the Martian environment’s potential for preserving ancient traces of life.

Morgan Cable, the deputy principal investigator of PIXL at NASA’s Jet Propulsion Laboratory (JPL), highlighted the significance of the fine-grained silica discovered on Mars. Drawing a parallel to Earth, Cable explained that such silica is often associated with past sandy environments—a setting where remnants of ancient life could be preserved and potentially discovered later. Perseverance’s advanced instruments, equipped to detect microscopic, fossil-like structures and chemical alterations indicative of ancient microbes, have not yet identified concrete evidence for either on the Red Planet. The ongoing exploration, however, holds promise for further revelations in the quest to unravel Mars’ geological and potentially biological history.

During its examination of another targeted site named “Ouzel Falls,” PIXL, the analytical instrument on Perseverance, identified the presence of iron linked with phosphate. Phosphate holds critical roles as a component of DNA and cell membranes in all known terrestrial life, forming a vital part of molecules involved in cellular energy transport. In response to PIXL’s insightful findings on these different rock patches, the mission team instructed the rover to collect rock cores in close proximity to the analyzed sites. Specifically, the samples from “Lefroy Bay” were collected near “Bills Bay,” and “Otis Peak” was obtained adjacent to “Ouzel Falls,” further enriching the diverse collection of Martian geological specimens.

Morgan Cable, the deputy principal investigator of PIXL at NASA’s Jet Propulsion Laboratory, emphasized the significance of the conditions identified by Perseverance, stating, “We have ideal conditions for finding signs of ancient life where we find carbonates and phosphates, which point to a watery, habitable environment, as well as silica, which is great at preservation.” Despite the substantial achievements, Perseverance’s mission is far from completion.

The ongoing fourth science campaign aims to explore the margin of Jezero Crater, near the canyon entrance where a historic river once inundated the crater floor. Notably, rich carbonate deposits along the margin, resembling a ring within a bathtub in orbital images, present promising avenues for further exploration and scientific discovery.

About the Mission.

The primary focus of the Perseverance rover’s mission on Mars is astrobiology, with a key emphasis on searching for signs of ancient microbial life. In addition to this, the rover aims to characterize Mars’ geology and past climate, laying the groundwork for future human exploration of the Red Planet. Perseverance holds the distinction of being the first mission to collect and store Martian rock and regolith (broken rock and dust). Following this groundbreaking mission, subsequent collaborative efforts between NASA and the European Space Agency (ESA) will involve sending spacecraft to Mars to retrieve these sealed samples from the surface, ultimately bringing them back to Earth for in-depth analysis.

The Mars 2020 Perseverance mission is an integral part of NASA’s Moon to Mars exploration strategy, aligning with the broader goals of preparing for human exploration of Mars. The Jet Propulsion Laboratory (JPL), managed by Caltech in Pasadena, California, played a pivotal role in building and overseeing the operations of the Perseverance rover.