Preparing to visit exotic locales is always a challenge.
What should you wear? What sights should you see? Without a guide, will you even know what you're looking at?
When geologists packed up their robotic surrogate, Spirit, for its trip to Mars, they sent it off with all the gear and know-how they thought it might need.
For The Record
Los Angeles Times Friday January 16, 2004 Home Edition Main News Part A Page 2 National Desk 1 inches; 32 words Type of Material: Correction
Radiation on Mars -- A article in Thursday's Section A incorrectly stated that Mars had a highly radioactive environment. It should have said that Mars' environment was exposed to high radiation levels.
But Mars has tricked them before.
Previous missions have brought back a wealth of information -- most of it contradictory. It's wet, it's dry; it's fertile, it's barren; the sky is blue, no, pink; it's geologically active, it's dead.
Spirit was scheduled to roll off its lander after midnight this morning. As the rover begins to wiggle its wheels for the first time in the fine Martian sand, the scientists will find out how well they've done as alien outfitters.
"Mars can absolutely fool us," said Steve Squyres, leader of the project's science team. "The way you design not to be fooled is to have several sensors that can look at the story from different directions, corroborate the evidence."
Each instrument on Spirit is designed to check up on the others: nine eyes with color, 3-D, X-ray and infrared vision; a long arm (with fingers) to reach out and touch things; a microscope; two particle detectors; and a diamond grinding tool that sharpens itself like shark's teeth (and even cleans up after itself).
Of course, there are two parts to touring: accurate observations (did you bring your glasses?) and interpretation (what is that thing, anyway?).
While today Mars is clearly "a miserable place," Squyres said, it has many geological features that suggest a more interesting (warmer and wetter) past. But the evidence so far has been ambiguous and confusing.
The job of Spirit and its twin, Opportunity, which is scheduled to land on Mars Jan. 24, will be to collect enough data to help set the story straight.
Spirit has already been busy scoping out the terrain.
The rover's panoramic camera (Pancam) has 20-20 vision, and it sees better than humans in 3-D.
Human stereo vision depends on the separation between our two eyes, which see slightly different views.
Pancam's eyes, however, are wider apart, allowing it to see in depth to greater distance.
Another remote sensor, the Mini-Thermal Emission Spectrometer (Mini-TES) has been checking out the scene in infrared -- a band of the electromagnetic spectrum that penetrates surface dust and detects the presence of minerals.
Mini-TES sits on the opposite side of the camera bar from the Pancam, giving Spirit eyes in the back of its head.
To compare images of the same scene from two spectral vantage points, the rover takes one image, swivels its head around and takes another.
Pancam and Mini-TES are giving mission scientists all the information they need to pick destinations for Spirit as it heads for the rocks.
To a geologist, the mute Martian rocks speak volumes about where they've been and what they've been through. Did the minerals form in water? Are there rounded grains of sand, worn smooth by water? Do layers tell of successive deposits in the past -- perhaps in a long-standing lake?
"I've never met a rock that lied to me," said James Garvin, lead scientist for the Mars exploration program at NASA headquarters. "If you read the rocks, you will not be duped."
Close reading requires close contact, and so Spirit is built to move. Using half a dozen hazard-avoidance cameras, an internal navigation system and six wheels that are powered by independent motors, the rover is designed to maneuver itself around rocks, getting itself from place to place with minimal instructions from Earth controllers.
"The philosophy is that for anything critical, the vehicle has to be smart enough to protect itself," said engineer Jennifer Trosper, who's in charge of the rover's travels on the ground.
Spirit is designed to be cautious. "We make it less cautious as we learn about driving on Mars," Trosper explained. Once the rover proves it can be trusted to make the right decisions, mission controllers will remove some programmed protections, rather like parents extending a curfew.
After reaching its target, Spirit will extend its 3-foot titanium arm -- which just happens to be exactly the length of Squyres' arm ("to the centimeter," he said).
Instruments for hands-on investigations sit at the tips of its fingers.
The arm has a shoulder (with two motors; think of them as muscles); an elbow (one motor); and a wrist (two motors).
Each "finger" has a feeler that signals Spirit's computer when contact has been made. The first task might be a bit of housekeeping -- scraping off accumulated rust and dust that camouflage the true nature of rock underneath.
A human geologist would get inside the rock by taking "a big ol' hammer" and whacking it, Squyres said. Safety goggles are recommended.
The rover has to take a subtler approach. Spirit carries a RAT, or Rock Abrasion Tool, that can drill a 2-inch-diameter hole about the depth of a tooth filling. Tiny brushes clear away the debris.