VOA科学技术2024--NASA Rover Captures Rock Showing Possible Signs of Microbial Life（在线收听）

A Mars explorer operated by the American space agency NASA has captured a rock that scientists say shows possible signs of ancient microbial life.

NASA said in a recent statement that the Perseverance explorer, or rover, collected the rock on July 21. Scientists working on the Perseverance team nicknamed the rock "Cheyava Falls," after the tallest waterfall in the Grand Canyon.

The rover's exploration area is believed to include a former river valley measuring about 400 meters wide. The valley is thought to have formed by water rushing into Jezero Crater billions of years ago. Scientists believe the area around Jezero Crater contained large bodies of water in the distant past.

NASA's statement says the rock shows signs of "chemical signatures and structures that could possibly have been formed by life billions of years ago..."

NASA team members based their findings on examinations of the rock with imaging equipment and multiple scientific instruments. But they noted that additional research is needed to confirm a history of microbial life.

The examinations did suggest the rock contains "organic compounds," NASA said. But the statement added, "While such carbon-based molecules are considered the building blocks of life, they also can be formed by non-biological processes."

Perseverance uses its robotic arm and drilling equipment to capture rock and soil samples from the Martian surface. So far, it has collected 22 samples. The rover has secured the samples in special containers and they are to be picked up and returned to Earth during a future mission.

Ken Farley is a project scientist with the Perseverance team at Caltech in Pasadena, California. He said, "Cheyava Falls is the most puzzling, complex, and potentially important rock yet investigated by Perseverance."

Farley said unusual color spots and other structural elements in the samples suggest "chemical reactions" that might have given energy to ancient microbial life. But he noted that so far, scientists have not been able to identify exactly how the rock formed.

The team described the rock as containing white veins that may have been created by the substance calcium sulfate. Between the veins, examiners found lines of material with a reddish color. These lines suggest the presence of hematite, a common substance found in many rocks on Earth.

David Flannery is an astrobiologist and member of the Perseverance science team from the Queensland University of Technology in Australia. He said that on Earth, these kinds of rock elements are often linked "with the fossilized record of microbes living in the subsurface."

The scientists said the new findings strengthen existing evidence that such rocks may have been created or were changed by flowing water on Mars billions of years ago.

Caltech's Farley said the rock sample had already been imaged and examined with lasers, X-ray equipment and other instruments as much as possible in recent weeks. He noted that Perseverance has done as much as it can to examine the newly discovered samples.

Farley added, "To fully understand what really happened in that Martian river valley at Jezero Crater billions of years ago, we'd want to bring the Cheyava Falls sample back to Earth." That way, he said, "it can be studied with the powerful instruments available in laboratories."

Words in This Story

nickname - n. a name used informally instead of an official name

crater - n. a hole left in the ground by an object that hits it with a huge force

signature - n. a feature in the appearance or qualities of a natural object

drill - v. to make a hole in a hard substance using a special tool

puzzling - adj. difficult to understand or figure out

vein - n. one of the thin lines found on an object

fossil - n. part of a plant or animal from many years ago that has been preserved in rock