LOS ANGELES  – Robert Zemeckis' performance capture system, which turns life-action into animation, gets quite a workout in Disney's "Mars Needs Moms," which opens on Friday.

Its characters, both human and Martian, tumble through space, slide down chutes, chase along corridors that turn every which way and dance around mountains and into caverns created out of huge mounds of trash. The process has also lost those weirdly inhuman faces that plagued "The Polar Express," Zemeckis' first foray into performance capture. In fact, so many things in this unique kind of animation, especially the designs and all its many details, keep getting better and better. So why does "Mars Needs Moms" feel so slight?

Other than "Beowulf," his most successful performance-capture film to date, Zemeckis has chosen to deploy this system in children's films. Which is just fine as far as that goes, but where the technical advances and story sophistication in his "Beowulf" pointed toward James Cameron's "Avatar," "Mars Needs Moms" points toward a ride at Disneyland.

This film from Zemickis' ImageMovers Digital and, appropriately, Walt Disney Pictures will certainly be a treat for younger family members. But for teens on up the generational scale, the interest level will plummet.

For that matter, it will be interesting to see how "Mars" in its first week fares against "Rango," an animated film with considerable sophistication and outreach to older audiences, in its second weekend. As with his "A Christmas Carol" movie, Zemeckis paints himself into a digital corner by ignoring adults.

"Mars" does do one thing much better than "A Christmas Carol," however: It has emotions. After all, it is based on a children's novel by cartoonist Berkeley Breathed, who admits the book came in reaction to a disobedient son expressing keen dissatisfaction with even having a (nagging) mother. Consequently, the entire story about a mom kidnapped by Martians and her rescue by her young son bubbles over with emotions. It's an illustrated laundry lists all the things moms do for their kids -- and that would include the laundry.

For this film, Zemeckis turns directing chores over to Simon Wells, who directed "The Time Machine" and co-directed the animated "The Prince of Egypt." Wells and his wife Wendy adapted the Breathed book with nearly every plot turn driving home the point that kids need moms.

Milo, age 9, is the focal point. He is enacted by Seth Green and voiced by a much younger Seth named Seth Dusky, age 11. The estimable Joan Cusack is Mom but since she spends most of the time under lock and key, the major roles fall to an extremely funny Dan Folger as Mars' only other human, a disheveled techo-wiz named Gribble; Elisabeth Harnois as Ki, a rebellious young Martian who learned English watching '70s sitcoms; and Mindy Sperling as the humorless, nasty Martian leader whose body appears as mummified as her heart.

Designer Doug Chiang has a grand time turning the Red Planet into a giant fun ride from those loopy Martians with triangular heads, no real noses and otherworldly bodies and gaits to an underground world of stark simplicity and sterility. Women run the place while men -- Gribble calls them the Hairy Tribe Guys -- get tossed down chutes with the garbage as they're apparently the most expendable resource on the planet.

The entire movie is set up as a race against the clock by Milo to save his mom but the film finds time to take in the Martian civilization in passing, a gag-filled and mostly lighthearted re-imagining of our own world if women ruled. (It is odd though how a movie meant to glorify moms is so riddled with anti-feminist concepts. These are, of course, Martian females not human ones but still ...)

Anachronistic dialogue rules for the most part as not only does Ki brim with the hep lingo of the Flower Children era, but Gribble, who is thirty-something, is stuck forever in the '80s when he left planet Earth.

The movie shrugs off any real attempt at science fiction other than oxygen helmets for the surface of Mars. The characters still dash around those surfaces in short sleeves in what should be an 87 degrees climate and make the round trip from Earth to Mars, which should take about 18 months, in a half minute.

The skill level of this motion capture animation is getting better all the time. So "Mars" is accomplished at every level. But the three most important things in movies are story, story, story so the movie never comes off as the considerable achievement it truly is.