During his rare breaks from the Athena science team’s final preflight preparations for next month’s launch, Squyres enthusiastically and affectionately talks about the rovers, barely taking a breath or pausing. The rovers, sitting in a building only 100 yards from Squyres, have been a labor of love, first envisioned in 1995.
“I feel like a 16-year-old kid with my first car, my first two cars, with these things. You use a word like ‘love’ advisedly when you are talking about a hunk of hardware, but boy I love these machines,” he says.
Standing 1.6 meters
high and weighing 179 kilograms, each twin rover resembles a human more than
a car — a 5’2”, 395-pound wheeling human. Each robot is outfitted
to conduct geology while weathering the harsh martian environment. “We see them as extensions of ourselves as geologists and scientists into this very alien, very distant environment — a way to see and feel and touch and learn about that environment and do science just like geologists would if they were there,” says Squyres, who started his career path as a field geologist.
Researchers hope to learn more about Mars’ past habitability, including its climate and hydrologic system. “Mars today is really cold and dry and barren, but if you look at the geologic record that seems to be apparent from orbit, it tells us about a different story of what Mars was like a long time ago,” Squyres says. They needed to find the right tools to read the geologic record and interpret the environment.
Visit this the Athena science team Web site to learn more about the Mars Exploration Rovers and to download images. Image courtesy of JPL/NASA.
So, Squyres’ team set out to build a flexible vehicle with a payload equivalent to the “toolbox” of a field geologist — 20/20 vision, a hand lens and a rock hammer, to name a few. But unlike a human field geologist, the two rovers have a diverse team of 120 scientists and engineers deciding for them how and when to use those tools — it’s strength in numbers. “Normally when you’ve got a geologist out in the field, it’s one person or maybe two working together; they don’t necessarily have that encyclopedic knowledge of the environment that they’re working in as a team this big and accomplished has,” Squyres says.
Among the team is Ray Arvidson, deputy principal investigator for the project. A veteran of Mars research, Arvidson began his mission to the Red Planet in 1969 when trying to choose between a graduate program in either marine geology or planetary geology. His decision became clear when Tim Mutch recruited him to work on the Viking Lander mission, which Arvidson worked on at Brown University up until 1982. After exploring other lines of planetary research, he returned to Mars following the Pathfinder mission, field testing two generations of rovers, Rocky VII and Fido.
In 1995, he and Squyres submitted competing proposals to NASA in a bid that ultimately went to the later-doomed Polar Lander mission. They decided to join forces later that year for what would become the Mars Exploration Rover mission. “We’ve been through various incarnations of mission proposals and funded activities, which all led to this pair of rovers that will touch down on Mars in January 2004,” Arvidson says.
Squyres is primarily the hardware guy and Arvidson the operations guy, defining the rovers’ scientific experiments. Arvidson, for example, thinks about ways to explore the planet’s subsurface: “The rover has six wheels, and you can imagine that if we lock five of them and let one of the two front wheels spin backwards, we can actually get into the soil,” he says.
The expertise of Arvidson and the rest of the Athena team will guide the rovers through countless scenarios every day. They will be on 24/7 watch — well, 24 hours and some change running on Mars time. A martian day, or Sol, is 24 hours and 39 minutes long.
“If a planning meeting starts at noon today, then tomorrow it starts at 12:39, the next day at 1:18 and two weeks later, it’s in the middle of the night,” Squyres says. And with the two rovers working in different time zones, switching back and forth between working on them could create “martian jetlag” for their Earth operators.
At a daily strategic meeting, Squyres and others will present and analyze the prior Sol’s data to decide what to do with the rovers next — where to send them, which rocks to sample or what instrumentation to use. The time delay created by the large distance between Earth and Mars means that operators cannot just “joystick” the rovers through Mars. Only a single set of instructions will command the rovers each day. And the rovers themselves can travel only 100 meters at most in one Sol.
Watching the field geologists on his team come to grips with some of the rover’s intrinsic drawbacks, Squyres says, has been an interesting process. “Initially, they get very frustrated. It takes a day to drive over to a rock instead of being able to walk over there in 30 seconds. But after they’ve begun to realize some of the power of these tools — the ability to do elemental chemistry like you can do in a laboratory right there in the field, the ability to look across a valley 500 meters away and tell what a rock is made out of without going over and touching it — they see it’s really cool,” he says.
While the scientists on Earth are busy planning for the next Sol, the rovers themselves will be sleeping — their batteries and protective outer layer keeping them warm during nighttime temperatures that can get as low as 96 degrees below zero Celsius. Solar-powered, the rovers will awake with the sunrise and receive a complex set of instructions, carefully tested and verified the prior martian night.
Although touring the Red Planet will be slow for the rovers, which will only be awake for about six hours each Sol, they will give us earthlings a whole new view of Mars. “We’ll be on the surface in two places, roving every few Sols or so; there will be new vistas to look at,” Arvidson says. “It really is a discovery process, because we have ideas of what we’re going to find, but they may be thrown out the window the first day we’re on the planet.”
Enabling the rovers to see what has never been seen, in part, is the 360-degree rotating Pancam Mast Assembly, which gives them a human field geologist’s 20/20 vision through two panoramic cameras. With 20/20 vision, the rovers can safely recognize obstacles about the size of a wheel diameter, the largest they can manage, out to a distance of about 100 meters. But, unlike any human field geologist, these rovers can look into the distance to “see” what a rock is made of using the vehicle’s infrared spectrometer.
Perhaps most humanlike is the design of the rover’s arm. “The distance from the shoulder to the elbow and the elbow to the wrist is within a centimeter or two of the exact dimensions of my arm,” Squyres says. The arm features a suite of some standard and some not-so-standard geologic tools for studying the planet’s rocks and soils, including the Microscopic Imager, a geologist’s hand lens for getting close-up views; the Rock Abrasion Tool, a glorified grinding rock hammer; the Mössbauer Spectrometer for analyzing iron-bearing minerals; and the Alpha Particle X-Ray Spectrometer for elemental composition analysis.
After their day in the field, grinding some rock or chemically analyzing some soil, the rovers will downlink data to Earth. The decision-making process will start again — continuing day after day for about 90 Sols, the estimated lifespan of the rovers.
And then, “one morning the sun is going to come up and the rover’s not going to talk to us,” Squyres says. Exactly when that day will come depends on unpredictable environmental factors. During the day, the rovers’ wing-shaped solar array will charge up the batteries to heat the robots at night. After time, dust will build up on the solar arrays and they won’t be able to charge the batteries any more. The rovers will fail. They will become part of Mars.
After Squyres and his team close up the first rover, known now only as MER-A, and put it inside its lander, they will never see it again — except as a little dot in pictures from the Mars Reconnaissance Orbiter scheduled for launch in 2005. “We’ve been pouring our hearts and souls into these things for years now, and we’re going to strap them on top of two rockets and that’s it,” he says.
Squyres’ break is over and he has to get back to preflight rover testing. He and his team are working long hours getting the rovers ready for launch, but their mission is really just beginning. All of this time for the rovers has meant sorely missed time away from home with his wife and two daughters, ages 12 and 15. “I’ve been doing this basically their whole lives, at least as long as they can remember,” he says. But on June 6, they will join him at the Cape Canaveral launch pad to watch his hunk of hardware head to Mars.
Links:
JPL Mars Exploration Rovers site
Athena science team site
