Follow this link to skip to the main content
National Aeronautica and Space Administration
+ NASA Homepage
+ NASA en Español
+ Marte en Español
Go Search
NASA's Mars Exploration Program
Overview Science Technology Missions People Features Events Multimedia All About Mars
Mars for Kids
Mars for Students
Mars for Educators
Mars for Press
+ Mars Home
List of All Features
Narrowing the Options

Major constraints dramatically narrowed down the territory on Mars that could even be considered. The candidate regions chosen, each comprising an area about the size of Southern California, exist below a certain elevation to provide enough atmosphere for the lander's parachute to descend properly. The sites also sit in a largely equatorial latitudinal band where enough sunlight shines to keep the solar-powered rovers supplied with electricity. Areas dominated by steep slopes, such as ravines or crater walls, are ruled out as hazardous to the lander and rover.

Reducing the Risk to the Airbags

Next to be eliminated were areas with large rocks. A rock larger than about one-half meter high, or knee-high to most people, is too tall for safety reasons. If the landing airbag system bounced hard on a rock that size, the rock might protrude high enough inside the airbags to damage the lander. Shorter boulders are considered acceptable, because even in the event of a direct bounce on top of one, the rock would not be tall enough to impinge on the lander inside.

But using even the highest-resolution images available to search for sites dominated by right-size rocks, said Golombek, "you can't guarantee there won't be bigger rocks. You can't eliminate them." With vigilant study and deduction, however, "you can try to make smaller the probability of landing on one."

Beware of Stealthy Terrain and 'Foo-foo Dust'

Laser altimeters will gauge the lander's altitude during descent in order to fire the solid rockets and deploy the parachutes and airbags at the right time. For those measurements to be made, the landers must be targeted to areas where the altimeter's radar will bounce back from the surface. Ruled out as landing sites are so-called "stealth regions".

"Stealth regions" are locales on Mars where the radar penetrates the surface but doesn't bounce back - a characteristic these regions share with the military's radar-avoiding stealth technology. In the case of Stealth fighters and bombers, the aircraft surfaces are made of a high-tech, radar-absorbing material. In the case of Mars' "stealth regions," however, the answer isn't known, said Golombek. They may be covered with a meter or more of "foo-foo dust," a Dr. Seuss-like term that Golombek uses to describe possibly fluffy accumulations of Mars' fine iron-oxide dust particles that can pile up in drifts like red snow.

In addition, "sending a solar-powered spacecraft to a dusty spot isn't a good idea. The stuff gets on the solar panels and reduces the power, gets stuck in the wheels and gears and generally gunks up the works" Golombek said.

<< Where to Land on Mars?
It's not as Easy as It Looks
Rocks: Too Much of a Good Thing >>

Full Text
Where to Land on Mars? It's not as Easy as It Looks
    Narrowing the Options
    Rocks: Too Much of a Good Thing?
    The Four Finalists and their Runners-Up

Credits Feedback Related Links Sitemap