Nasa regains contact with Mars lander

(AP)

Nasa's Phoenix Mars spacecraft regained contact with Earth today, more than a day after falling silent, but its days operating on the red planet are still numbered, mission chiefs say.

Waning sunlight and a dust storm this week drained the lander's power, forcing it to go into safe mode. It failed to respond to two wake-up calls from Earth on Wednesday and yesterday, but sent a signal early today when the orbiting Odyssey spacecraft passed overhead.

Phoenix is programmed with a "Lazarus mode" that automatically causes it to reboot itself after losing power. Though Phoenix answered the latest call, it went back to sleep for another 19 hours to recharge its battery. Engineers expect the lander to survive several more weeks.

"We knew this was coming. It's bittersweet," said project manager Barry Goldstein of Nasa's Jet Propulsion Laboratory.

During its three-month prime mission, the sun stayed above the horizon, allowing Phoenix to dig trenches in the soil and collect ice bits for its various instruments to analyse. Nasa extended the mission hoping to get the most science out of the spacecraft before it died.

In recent days, the weather at Phoenix's landing site has worsened. Overnight temperatures plunged to minus 141 degrees, and daytime temperatures reached only minus 50 - the lowest temperatures so far in the mission. The lander also battled a dust storm, which has drained its energy.

Phoenix landed in a patch of ice in Mars' high northern latitudes to study whether the environment could be friendly to microbial life. It has found evidence that the ice might have melted at some point, although the soil is dry.

It has yet to find the presence of organic, or carbon-based, compounds that are considered essential for life.