LOS ANGELES, Sept. 10 (Xinhua) -- Liquid water has interacted with the Martian surface throughout the planet's history and into modern times, NASA's Jet Propulsion Laboratory (JPL) said Thursday.
These recent findings are based on data about the planet's carbon dioxide, which makes up about 95 percent of the Martian atmosphere, according to the JPL, which is headquartered in Pasadena, California.
The data was collected by NASA's Phoenix Mars Lander, which arrived on Mars on May 25, 2008, but is no longer operating.
Phoenix precisely measured isotopes of carbon and oxygen in the carbon dioxide of the Martian atmosphere. Isotopes are variants of the same element with different atomic weights.
The research also provides new evidence that volcanic activity has persisted on the Red Planet into geologically recent times, several million years ago, the JPL said.
"Atmospheric carbon dioxide is like a chemical spy," said Paul Niles, a space scientist at NASA's Johnson Space Center in Houston. "It infiltrates every part of the surface of Mars and can indicate the presence of water and its history."
Niles is the lead author of a paper about the findings published in Thursday's online edition of the journal Science. The paper explains the ratios of stable isotopes and their implications for the history of Martian water and volcanoes.
"Isotopes can be used as a chemical signature that can tell us where something came from, and what kinds of events it has experienced," Niles said.
This chemical signature suggests that liquid water primarily existed at temperatures near freezing and that hydrothermal systems similar to Yellowstone's hot springs have been rare throughout the planet's past.
Measurements concerning carbon dioxide showed Mars is a much more active planet than previously thought. The results imply Mars has replenished its atmospheric carbon dioxide relatively recently, and the carbon dioxide has reacted with liquid water present on the surface, the JPL said.
