Mars Water Discovery Spurs Deeper Questions

Stefan Lovgren
for National Geographic News
March 3, 2004
NASA scientists said Tuesday that the roving robot Opportunity has found evidence that water once soaked the planet Mars.

Liquid water is the one absolute requirement for life on Earth. Although the discovery does not mean the evidence of life on Mars has been found, it suggests that life could have evolved there at one point just as it did on Earth.

The discovery may have laid to rest one of the most vexing questions in planetary science: whether Mars was once capable of sustaining some form of life.

But it has also prompted a plethora of new questions.

"If liquid water existed on Mars, did life develop there? What is required to form life? How unique is life on Earth?" said Matt Golombek, a geologist at the Jet Propulsion Laboratory in Pasadena, California, who was in charge of choosing the landing sites for the two rovers. "These are compelling questions that we can begin to address with a Mars exploration program."

El Capitan

The Mars mission was specifically launched to check if Mars ever had a persistently wet enough environment to host life. By landing the rover Opportunity next to an exposed slice of bedrock on the inner slope of a small crater in the Meridiani Planum region of Mars, the scientists hit the jackpot.

Pictures from the rover's panoramic camera and microscopic imager of the target rock, dubbed "El Capitan," revealed salt-laden sediments that would have been shaped by flowing water or maybe even a great Martian lake or sea.

The dense deposits of sulfates, which are similar to Epsom salts on Earth, are the key evidence that water once existed on Mars.

Pebble-like structures, which the scientists nicknamed "blueberries," were found embedded in the rock. The scientists have concluded that these were created from mineral deposits emerging from a watery solution inside the rock.

"Most of the evidence to date has been strongly suggestive, based on morphology, but perhaps not conclusive," said Golombek. "The evidence is in the chemistry and mineralogy [sulfates] and textural clues for thin bedding, relict minerals that have been dissolved away and the growth of concretions which requires liquid water."

Most Like Earth

Scientists will now attempt to learn if Mars had any standing bodies of water—lakes or even seas—or if the water simply bubbled up from underground. They will also try to find out when the water disappeared.

"Understanding liquid water's role on the Martian surface in the past is key to understanding whether Mars could have been an abode for life," said Bruce Betts, director of projects at the Planetary Society in Pasadena, California.

Mars is the planet in our solar system that most closely resembles Earth. It has a rocky surface, making it easier for life to gain a foothold. Some scientists believe primitive life could survive around hydrothermal vents near the planet's surface. Today it's perhaps too cold for life to exist there, but organisms may have thrived in the past.

"Liquid water isn't stable on the surface of Mars now, but existed on the Martian surface in the past," said Betts. "More water for longer periods in the Martian past would mean more chance, presumably, for life to evolve and exist."

Mars may have been not only wetter in the past, but could have had a denser atmosphere. There is the possibility that life arose on Mars, only to die out as conditions on the planet worsened. Some researchers have suggested that future searches for life be shifted to focus on extinct, rather than extant, life.

Manned Missions

On Earth, such extinct life can be found in the form of fossils dating from 3.5 billion years ago. But the rovers cannot date Martian rocks or detect mineral signatures left by living organisms.

While the new discovery proves that water once existed on Mars, the rovers cannot test the possibility that liquid water may still exist beneath the planet's surface.

Instead, the findings have prompted new questions of what happened to the water and atmosphere on Mars.

Scientists now hope the success of the latest mission will expand the Mars exploration program so that some of those questions can be answered. The rover missions have raised the possibility of sending a manned mission to Mars.

"Mars exploration rarely disappoints," said Betts. "It certainly didn't this time."

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