Space buffs can now visit Mars and feel what it must be like to explore the towering mountains, layered canyon walls, and meandering channels of the Red Planet without having to worry about its freezing temperatures and tenuous atmosphere.

With the help of Google Mars (mars.google.com) it is possible to soar over the grandest canyon in the solar system, Valles Marineris, visit the giant volcano Olympus Mons, which is three times taller than Everest, or inspect the landing sites for the two Mars rovers, Spirit and Opportunity.

Arizona State University and NASA’s Jet Propulsion Laboratory have also released a film on the Internet, Flight Into Mariner Valley, at themis.asu.edu.

It takes viewers on a simulated flight through Valles Marineris, which looks like a wound stretching one fifth of the way around Mars. It is 2,500 miles long – the distance to Los Angeles from New York- and four miles deep.

The simulated flight is made possible by a giant mosaic of Mars that combines more than 17,000 individual photos meticulously stitched together. The pictures were taken by Arizona State University’s Thermal Emission Imaging System, or Themis, a multi-band space camera aboard NASA’s Mars Odyssey spacecraft.

Google Mars also draws on information from instruments on the Mars Global Surveyor.

Although nothing like as high resolution as Google Earth, it does give a resolution down to that of a football field, according to one of the Arizona team, Greg Mehall, which is remarkable given that it is based on images taken from an altitude of 250 miles.

The images in the giant Themis mosaic were taken by infrared light and reveal details as small as 750 feet across.

They provide a unique view of Mars, melding day and night images. Areas that are cooler appear in darker tones, while warm regions and features appear light-colored.

Several areas of Mars with special interest for scientists can be explored in even more detail using the infrared mosaic at Google Mars.

“Valles Marineris – or Mariner Valley – is the kind of place where scientists want to look at both the small details and the big picture,” an Arizona planetary geologist, Professor Phil Christensen, said.

“It’s more than just a spectacular sight – it’s also a geological history book of Mars that we’ve finally begun to open and read.”

Yesterday, British scientists celebrated the news that another probe, NASA’s Mars Reconnaissance Orbiter, appears to have smoothly entered Mars orbit.

Scientists from Oxford, Cardiff, and Reading Universities are involved in the Mars Climate Sounder instrument – essentially a weather station for Mars.

[Also yesterday, the Associated Press reported that NASA postponed the launch of space shuttle Discovery from May until at least July because a faulty fuel tank sensor. A similar problem briefly delayed last summer’s launch of Discovery on the first shuttle flight since the Columbia disaster in 2003.

NASA said it needs the time to open up the spacecraft’s hydrogen fuel tank and replace the sensor, which gave an electrical resistance reading that was slightly off. The space agency plans to replace the three other sensors in the tank, too, to be safe, the wire service reported.]