BIG ROVER PLANNED FOR MARS.

Byline: Usha Sutliff Staff Writer

PASADENA - NASA announced Thursday it will send to the Red Planet a larger cousin of the Mars Pathfinder rover - built almost entirely at the Jet Propulsion Laboratory - for a science mission in 2003.

The roughly $350 million rover, tentatively dubbed Mars Explorer 2003, will carry a sophisticated set of instruments enabling it to search for the liquid water that may have been part of the planet's past and study the geological building blocks on the surface.

``This is loaded with scientific instruments. It is the first time NASA has done Mars mineralogy, ever. In essence, this thing is a robotic geologist,'' said Firouz Naderi, Mars Program manager at JPL. ``This is the future. The future is to land on Mars and do science.''

The rover will weigh about 330 pounds and will be able to trek up to 330 feet across the surface each Martian day - 24 hours and 37 minutes. The Mars Pathfinder Sojourner rover, which had less mobility and scientific capability in comparison, weighed a mere 24 pounds.

Naderi used a terrestrial reference to make his point.

Los Angeles Lakers player Shaquille O'Neal weighs the same as the 2003 rover, he said, while the Pathfinder Sojourner weighed what the towering basketball player probably weighed ``when he was about 2 years old.''

The rover will be launched on top of a Delta II rocket and after a cruise of 7 1/2 months will enter the Martian atmosphere Jan. 20, 2004, according to NASA.

The rover's landing will use the same ``drop, bounce and roll'' technology that captured the imagination of the public and the science world alike during the Mars Pathfinder mission in 1997.

That JPL-managed mission made history when its lander hit the Martian atmosphere at about 17,000 mph and used a huge parachute to slow it down.

A giant cocoon of air bags inflated to cushion its landing and then, like a giant rubber ball, the Pathfinder bounced and rolled around before coming to rest on Mars' surface.

With the Mars 2003 mission, the spacecraft will bounce about a dozen times and could roll as far as a half-mile, NASA estimates. When it comes to a stop, the air bags will deflate and retract and the ``petals'' will open, bringing the lander to an upright position and revealing the rover, according to Naderi.

The exact landing site has not yet been chosen but will likely be a place where scientists suspect there may once have been water such as a former lake bed or channel deposit.