Scientists were making efforts to contact the non-responsive Spirit Mars rover, which has lost contact with Earth during the Martian winter prompting fears that it might be permanently lost.

NASA's Jet Propulsion Laboratory said Friday that it began paging the rover this week with a series of beeps that demand a response from Spirit.

Scientists, however, expect the rover to be unable to answer for several months because low solar battery power has likely put it into hibernation mode during the winter, which runs from May to November.

Spirit has not phoned home since March 22.

Researchers think it could contact them within the next several months, but admit they may never hear from Spirit again. They said if they have not heard from it by March 2011 they will likely give Spirit up for lost.

'This has been a long winter for Spirit, and a long wait for us,' Cornell University scientist Steve Squyres said. 'Even if we never heard from Spirit again, I think her scientific legacy would be secure. But we're hopeful we will hear from her, and we're eager to get back to doing science with two rovers again.'

NASA said in January that Spirit had reached its final destination after the failure of efforts to free the space probe from sandy soil where it had been trapped for months. The rover was to live out its life as a stationary science platform.

Spirit is one of two rovers that have far exceeded expectations and are now in their sixth year of what were planned as 90-day missions, exploring the Martian surface and making important discoveries about water on Earth's neighbour.

Spirit landed Jan 3, 2004, and was followed by sister rover Opportunity three weeks later. Since then, the golf cart-sized craft have provided scientists with valuable information about the Red Planet's wet history, while sending back 250,000 images and driving more than 21 km.