CNN VIEWERSHIP ENTERS NEW FRONTIER.

Byline: Janet Weeks Daily News Staff Writer

Mars is barren and desolate and covered with big rocks - much like the San Fernando Valley hillsides that used to pass for planets on the old ``Star Trek'' TV show.

Maybe that explains why so many people are mesmerized by Mars, so much so that images from Pathfinder shown on CNN on Friday boosted the cable network to its highest Fourth of July ratings in a decade, since the Iran-Contra hearings.

Between 5 p.m. and 5:30 p.m. on Independence Day, 1.4 million households tuned in to CNN to see pictures of the pinkish planet, perhaps hoping Capt. Kirk would jump out from behind a boulder, flip open his communicator and demand to be beamed up.

CNN correspondent John Holliman, who has been covering the Pathfinder mission, says he thinks the exploration of Mars fascinates many because Americans are adventurers by nature.

``There is something in the American spirit this rouses,'' he says. ``We want to go places that people haven't been and look around.''

The fact that Jet Propulsion Laboratory scientists in Pasadena are hipper and younger looking than the Apollo-era scientists also attracts younger audience members, Holliman theorizes.

``The people working on this project are younger and more energetic and more pumped. All of these guys are younger than I am. There's not a tie in the room at the JPL . . . and very few socks.''

In any case, the timing of the Mars landing - from a marketing perspective - just couldn't be better, coinciding as it does with America's current outbreak of space fever. Consider the facts:

``Men In Black,'' the sci-fi comedy about aliens on Earth, was No. 1 at the box office last weekend and broke last year's Fourth of July record, set by ``Independence Day,'' another aliens-on-Earth film.

People convinced of the existence of UFOs gathered last weekend in Roswell, N.M., for a 50th anniversary of the mysterious ``incident.'' Some believe the government found an alien craft in the desert and is engaged in a five-decade conspiracy to deny such a discovery.

``Contact,'' a film based on a Carl Sagan novel about a radio astronomer who connects with extraterrestrial life, opens to much hoopla Friday.

And then there's Pathfinder on Mars, which, over the weekend, boosted CNN's ratings by 100 percent over the news channel's viewership for June, according to Howard Polskin, vice president of public relations for CNN.

``The ratings were out of this world, if I may use the pun,'' Polskin says. ``This is what television does best - bring you someplace you can't be physically. It's almost a miracle to be in your living room watching Mars.''

The ratings are even more impressive considering that most people celebrate July 4 with barbecues and beach parties, which usually causes viewership to decline.

And TV isn't the only place where people are checking out Mars. CNN's World Wide Web site - which carries information on the Pathfinder mission - received more hits on Independence Day than any day since the night of the presidential election in November.

Viewers also watched Mars on C-SPAN, a channel that typically broadcasts Congress as a public service of the cable industry. Since C-SPAN doesn't track ratings - fearing such information would skew what it covers - there's no way to gauge how many people are watching Mars on the channel, says spokeswoman Anne-Marie DiNardo.