LOS ANGELES (AFP) — An asteroid hurtling towards Mars has a one in 75 chance of chance of scoring a direct hit on the red planet next month, NASA experts said in a statement Friday.

The US space agency's Near Earth Object Program (NEOP) revealed that the asteroid's exact course was difficult to predict, but said it could slam into Mars on January 30, leaving a crater measuring an estimated 1 kilometer across.

If the asteroid, which has been named 2007 WD5, missed Mars as expected it could return to swing past Earth years or decades later, but there was no indication of a threat to the planet, scientists said.

A collision with Mars would be likely to send an enormous dust cloud into the planet's atmosphere.

The exact path of the asteroid, which was discovered in November by the NASA-funded Catalina Sky Survey near Tucson, Arizona, was becoming increasingly difficult to observe because it was receding from the Earth, scientists said.

The asteroid, believed to measure around 50 meters (160 feet) across, had already passed within 7.5 million kilometers (5 million miles) of Earth in early November.

Scientists believe sulphur dioxide released from ancient volcanoes created a balance similar to Earth's carbon cycle, which controlled the climate. 

The notion, outlined in the journal Science, could explain why Mars rovers have found sulphur minerals on the surface but no limestone like on Earth. It may also provide clues to how life evolved on our own planet. 

"Before the origin of life, our atmosphere may have looked much like early Mars," said Daniel Schrag, lead author of the Science paper. "Sulphur dioxide may have had an important role then as well."
Specifically, researchers now suggest that ancient volcanoes could have released brimstone — now more commonly known as sulfur — that warmed up the red planet enough for liquid water oceans in the early days of Mars. These findings might also shed insight on the young Earth, including the origins of life, scientists added.

Evidence of liquid water on the surface of Mars roughly 3.8 billion years ago implies that although its surface temperature now averages -51 degrees Fahrenheit (-46 degrees Celsius), it was once relatively warm. Scientists have often proposed the red planet was enveloped during its youth in an atmosphere rich in carbon dioxide. Carbon dioxide is a "greenhouse gas," meaning it traps heat from the sun, warming up worlds such as Earth.

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