VOA科学技术2024--New Evidence Suggests Large Water Ice Supply near Mars’ Equator（在线收听）

New Evidence Suggests Large Water Ice Supply near Mars’ Equator

　　A Mars explorer has discovered new evidence of a large amount of water ice buried near the planet's equator.

　　The discovery was made with data collected by the Mars Express orbiter. The spacecraft is operated by the European Space Agency (ESA). The American space agency NASA is a partner on the orbiter's mission.

　　ESA launched Mars Express in 2003 and it has been studying the Red Planet ever since. The mission's main goal is to use its seven scientific instruments to search for signs of water underneath the surface of Mars.

　　Scientists involved in the new research say data suggesting the presence of newly discovered ice deposits could mean Mars may have once supported life.

　　The Mars Express orbiter collected data around an area of the planet known as the Medusae Fossae Formation (or MFF). NASA describes this formation as "a soft, easily eroded deposit that extends for nearly 1,000 kilometers along the equator of Mars."

　　Scientists believe the MFF was most likely formed by wind-blown dust or volcanic ash. The formations could have formed after volcanic activity estimated to have taken place up to 3.8 billion years ago.

　　Images of the area show raised areas that scientists thought in the past might contain dust blown around the planet by wind over many years. But the new research used newer data collected by the orbiter's MARSIS instrument. It is "a subsurface radar sounder" with a 40-meter-long antenna. The tool looks for water on the surface, as well as up to five kilometers below the surface.

　　The MARSIS instrument is designed to send radio waves to an area scientists choose. It then attempts to listen to and examine "echoes" produced by the radio waves. The echoes help researchers recognize where water or ice might be, NASA explains.

　　Scientists say any water identified near the surface results in stronger signals while the presence of ice or other materials would produce weaker signals. The team said MARSIS readings suggest the MFF area of Mars contains a large amount of water ice rather than wind-blown dust.

　　Thomas Watters of the U.S. Smithsonian Institution led the new research. His team's findings were recently published in a study in Geophysical Research Letters. He said in a statement the radar data showed the deposits in the MFF area were even thicker than earlier measurement estimates had shown.

　　The researchers said the data showed the examined deposits extended beneath the Mars surface to depths up to 3.7 kilometers. They seemed to contain "layers of dust and ice, all topped by a protective layer of dry dust or ash."

　　Earlier data examinations of the MFF area found similarities in the electrical properties of deposits there to ice-rich deposits found in the planet's north and south poles. The latest MARSIS data strengthens this evidence by suggesting similarities between deposit layering in the MFF and the planet's poles.

　　"The radar signals match what we'd expect to see from layered ice," Watters said. He added that the radar waves were found to be "similar to signals we see from Mars's polar caps, which we know to be very ice rich."

　　It is not the first time scientists have discovered strong evidence for the presence of water ice on Mars. But the researchers say the latest study suggests the largest amount of water ever identified in the MFF area. They estimated the total amount of water contained there would be enough "to cover the surface of Mars to a depth of about 1.5 to 3 meters."

　　Colin Wilson is a project scientist with the Mars Express mission. He said while the new finding is exciting, it also "raises as many questions as answers." He continued, "How long ago did these ice deposits form, and what was Mars like at that time?" Wilson said if confirmed to be water ice, the large deposits "would change our understanding of Mars climate history."

　　Watters added that since the discovery was made in an area near the Martian equator, it could be considered a good place for future exploration missions. He explained that with a lower elevation, the MFF area would be considered "an ideal landing spot for spacecraft." Such an elevation provides more atmosphere to support an effective, controlled landing, Watters said.

　　Words in This Story

　　equator –n. an imaginary line around the middle of a planet that is an equal distance from its north and south poles

　　mission – n. the flight of a spacecraft to perform a certain task or job

　　deposit – n. a layer of a substance that has developed from a natural or chemical process

　　erode – v. to gradually be damaged over time

　　antenna – n. a piece of metal used for receiving television or radio signals

　　echo – n. the repeating of a sound caused by the reflection of sound waves

　　layer – n. an amount of substance covering a surface

　　match – v. to fit together or make suitable for fitting together

　　elevation – n. the height of a place above the level of the sea