Mars Science Lab poised for trail-blazing mission
By WILLIAM HARWOOD
CBS News
In a $2.5 billion gamble, a nuclear-powered Mars rover the size of a small car will attempt a pinpoint landing near the base of a 3-mile-high mountain overnight Sunday to search for the building blocks of life and evidence of past or present habitability.
In so doing, the Mars Science Laboratory rover, dubbed "Curiosity" in a student naming contest, will climb layer by layer through vast eras of the red planet's enigmatic history, possibly shedding light on the transition from a warmer, wetter past to the drier, frigid world of more modern epochs.
Doug McCuistion, director of Mars exploration at NASA Headquarters in Washington, said the mission "could arguably be the most important event in the history of planetary exploration."
"It truly is a major step forward, both in technology and in potential science return and science capability to unlock the mysteries of Mars in places that have never been accessible to humankind in the past."
But getting there will not be easy.
The Mars Science Laboratory spacecraft must first endure entry temperatures of up to 3,800 degrees Fahrenheit, crushing deceleration of up to 15 Gs and the 65,000-pound jerk of a huge parachute inflating at supersonic velocity.
After slowing the spacecraft to a bit less than 200 mph, the parachute will be cut away and a rocket-powered descent stage, carrying the Curiosity rover bolted to its belly, will fall free for a nail-biting one-mile plunge to the surface.
Controlled by the rover's main computer, the descent stage will slow to just 1.7 mph, four of its eight rocket engines will shut down and Curiosity will be lowered on the end of a 25-foot-long tether like a bobber on a fishing line.
With the descent stage maintaining its slow fall, the rover's six wheels are expected to touch down on the floor of Gale Crater around 1:17 a.m EDT (GMT-4). Confirmation will be relayed back to Earth in near realtime by NASA's Mars Odyssey satellite.
But because of the distance between Earth and Mars -- about 154 million miles -- it will take 13.8 minutes for confirmation of a successful landing to reach anxious engineers and scientists at NASA's Jet Propulsion Laboratory in Pasadena, Calif. That translates into 1:31 a.m. on Aug. 6, Earth-received time.
"MSL holds the potential to look for evidence of habitable environments, if they existed, on Mars in the distant past," said NASA science chief John Grunsfeld, a veteran shuttle spacewalker. "The Curiosity rover has the potential to discover the building blocks of life on Mars, if life ever existed on Mars.
"However, the Curiosity landing is the hardest NASA robotic mission ever attempted in the history of exploration of Mars or any of our robotic exploration. This is risky business."
Curiosity's novel "sky crane" landing technique has dominated news coverage, in part because it seems so outlandish compared to past missions and because it appears riskier given a full-up, end-to-end test was not possible in Earth's atmosphere and gravity.
But engineers are confident the entry, descent and landing system will work as advertised, the first act in the most complex, expensive and scientifically significant robotic Mars mission ever attempted.
"This rover, the Curiosity rover, is really a rover on steroids," Colleen Hartman, a senior NASA manager, said before launch. "It's an order of magnitude more capable than anything we have ever launched to any planet in the solar system. It will go longer, it will discover more than we can possibly imagine."
Over the course of a planned two-year mission, Curiosity will act as a robotic geologist, using high definition cameras to photograph its surroundings in exquisite detail, beaming back wide-angle high-resolution panoramas as well as close-up microscopic views through what amounts to a geologist's hand lens.
Equipped with 10 state-of-the-art instruments and a sophisticated robot arm, the rover will drill into rocks and soil, use a rock-vaporizing laser to assess more distant targets and collect rock and soil samples for detailed chemical analysis.
The initial phases of the mission will be focused on the crater floor and an alluvial fan visible from orbit where scientists believe water may have pooled in the distant past.
But the long-range objective is Aeolis Mons, dubbed Mount Sharp by NASA, a huge wind-eroded mound of sedimentary rocks in the center of Gale Crater that rises more than three miles, higher than Mt. Rainier above Seattle.
The instruments aboard Curiosity were not designed to look for signs of life. Rather, the primary goal of the Mars Science Laboratory is to search for carbon compounds and evidence of past or present habitability.
"We are not a life detection mission," Grotzinger said. "The first and important step toward that is to try to understand where the good stuff may be."
Grotzinger would not give odds on finding carbon compounds in Gale Crater, but "the information from orbit looks so darn good ... I'd be surprised if we landed on the surface and didn't find something that looked like it could have been a formerly habitable environment.
"But if you're trying to get me to say what are the chances of finding organic carbon, I'd say it's like looking for a needle in a haystack, and the haystack is as big as a football field."
Searching for carbon compounds is only part of Curiosity's mandate. As it works its way up the 15-degree slopes of Mount Sharp and passes from older to younger layers, the rover is expected to cross over beds marking a geologically sudden transition from a warmer, wetter past to a drier, less hospitable age.
In so doing, hundreds of thousands to tens of millions of years of the planet's evolution will be brought into focus.
"The really cool thing about the Gale stratigraphic succession to me is it's a tour through nearly the entire history of Mars where we can begin to understand these major changes in the environmental history of the planet," Grotzinger said in a more recent interview. "And I can't think of another place on Mars where you can go do that."
To get a sense of the landing site's potential, Grotzinger said the layers making up Mount Sharp are three times thicker than those in the Grand Canyon, which "takes you ... through 300 million years of Earth history, from the origin of animals to the origin of dinosaurs."
"If you were to have remote sensing data from an orbiter around Earth, looking at Earth and the Grand Canyon 150 years ago, nobody would have ever predicted that that's what you would discover if you went there one day," Grotzinger said. "I don't know what it is that we're going to discover about Mars. But I have to believe it's going to be something really good."
The high-stakes mission comes at a critical time for NASA's planetary exploration program as budget pressures threaten to sharply reduce the scope of the agency's robotic missions.
The Obama administration's fiscal 2013 budget request calls for $17.7 billion for NASA, but it cuts $300 million from planetary science, most of it from the Mars program.
As a result, NASA has backed out of a 2008 agreement with the European Space Agency to share the costs of two ambitious Mars missions known as ExoMars, which called for launch of an orbiter in 2016 and two rovers in 2018.
Along with searching for signs of past or present life on Mars, the missions also would have tested technologies needed for a long-sought sample return mission.
"Tough choices had to be made," NASA Administrator Charlie Bolden said when the budget was unveiled earlier this year. "This means we will not be moving forward with the planned 2016 and 2018 ExoMars mission. ... Instead, we'll develop an integrated strategy to ensure the next steps in Mars exploration will support science as well as human exploration goals and potentially take advantage of the 2018 and 2020 exploration windows."
In the wake of the budget's release, Bill Nye, chairman of the Planetary Society, said the "priorities reflected in this budget would take us down the wrong path."
"Science is the part of NASA that's actually conducting interesting and scientifically important missions," he said in a statement. "Spacecraft sent to Mars, Saturn, Mercury, the Moon, comets and asteroids have been making incredible discoveries, with more to come from recent launches to Jupiter, the Moon and Mars. The country needs more of these robotic space exploration missions, not less."
In a rare show of bipartisan agreement, Rep. Adam Schiff, D-Calif., and John Culberson, R-Texas, whose states include NASA field centers, wrote in Space News that without congressional action, "the administration's cuts to planetary science would devastate America's planetary program."
"The robotic Mars program, one of our nation’s science jewels, faces the most severe cuts, including a rover mission to Mars in 2018 identified as the highest priority in planetary science in the most recent decadal survey," they wrote. "This would be a tragic loss for a program that has made major scientific discoveries and captured the interest of people around the world."
The Curiosity rover is the only so-called "flagship" mission currently in the Mars pipeline and it takes years to plan, design and build new spacecraft. Aerospace engineer Robert Zubrin, president of the Mars Society and author of "The Case for Mars," said in an interview that the fate of NASA's Mars program rests firmly on Curiosity's shoulders.
"This is a superb mission, if it succeeds," he said. "On the other hand, if it fails, it's the flagship out the window. That would be serious enough. But the stakes were upped this past February when the Obama administration canceled the 2016 and 2018 missions, and thus completely scrambled the program, completely set it adrift."
If Curiosity fails, he said, "not only do you lose this mission, but I think we lose the rest of the decade. On the other hand, if this succeeds, it will be a brilliant mission, it will be the best Mars mission ever flown and I think we have a real chance of not only reversing the missions that were cut but moving on towards sample return."
MSL Project Manager Pete Theisinger said in an interview that he was aware of the outside scrutiny and pressure to chalk up a success. But he said the MSL team was not distracted.
"Down in the trenches where the work's actually accomplished, people love what they do, they're very professional about it and they want to do the right job and so that's all they think about," he said. "It wouldn't matter whether it was this two-and-a-half-billion-dollar thing that's on the national stage or it was a $100,000 thing in the lab. They feel the same.
"When you get up to the top of the food chain, yeah, there's a feeling that this is a very visible mission, we know that, people like you don't call me if it's not a very visible mission. And so, we know that. But once again, the job is to get the job done and to do it in the best balanced, prudent approach that we can. I don't think we feel it, we just know it's there."
Launch originally was planned for 2009, but in 2008, the flight was delayed two years to verify the integrity of the myriad actuators used in the rover's mobility system and robot arm, a delay that added $400 million to the project's price tag.
Curiosity's journey finally got underway on Nov. 26, 2011, when a United Launch Alliance Atlas 5 rocket boosted the craft into space. The spacecraft has performed in near flawless fashion during the long cruise to Mars and now the stage is set for entry, descent and landing Aug. 6.
Acting as a robotic geologist, Curiosity is well suited for its trailblazing mission, dwarfing the hugely successful Spirit and Opportunity rovers both in size and scientific capability. The instruments carried by each of the earlier rovers weighed about 11 pounds. The 10 aboard Curiosity weigh 165 pounds.
Not counting its robot arm, Curiosity is 10 feet long, nine feet wide and seven feet high measured to the top of its main camera mast. Its mobility system is similar in design to that used by Spirit and Opportunity, but its six 20-inch-wide wheels are twice the size of the earlier models. Each wheel has its own drive motor and the four corner wheels are independently steerable.
Top speed is over hard, flat ground is about a tenth of a foot per second, although the rover typically will move at half that velocity when operating autonomously and using hazard avoidance.
The earlier rovers were solar powered, forcing them to shut down at night and to hibernate in winter months to conserve power and heat. MSL is powered by a radioisotope thermoelectric generator, using the heat produced by the decay of radioactive plutonium dioxide to generate electricity. Excess heat is used to keep electronics and other sensitive systems from getting too cold.
Curiosity is equipped with redundant computers, using one at a time and keeping the other as a backup. The computers feature radiation-resistant PowerPC 750 processors operating at 200 megahertz with two gigabytes of flash memory storage, about eight times more than Spirit and Opportunity.
The system was designed from the ground up to use the orbiting Odyssey and Mars Reconnaissance Orbiter satellites to relay engineering and scientific data back to Earth.
Independent of the weather and the sun, Curiosity is designed to operate for at least one martian year -- two Earth years -- and to rove at least 12 miles. But engineers expect it to continue operating well beyond its design specification, both in time and distance.
"You're asking a project manager how long it's supposed to live and you expect an answer?" Theisinger laughed. "We test these things, the mechanical or moving parts, we test for either two or three times life, usually three times life. So if we know a wheel is supposed to run for 20 kilometers, we'll test it to 60 kilometers.
"We don't test them to failure. All that we know is that we've tested the mechanisms for two or three times life and they all passed that test program. The RTG is good for a decade, 12 years, 15 years, something like that, before we really get into power issues. The battery is probably good for eight years. The electronics are high reliability electronics, but some of it is single string.
"It could last a long time if we haven't made a mistake," he said. "If Mars doesn't get us, it could last a long time."
The heart of the spacecraft is the most sophisticated instrument package ever sent to Mars.
The Sample Analysis at Mars, or SAM, instruments will be used to analyze soil and rock fragments delivered by the lander's robot arm. It includes a gas chromatograph, a mass spectrometer and a laser spectrometer to look for carbon compounds and measure isotope ratios, which will shed light on the history and distribution of water and the evolution of the martian atmosphere.
"You've got to have water for life as we know it," Grotzinger told CNET in an earlier interview. "The second thing is you need a source of energy. ... And then the important thing is, you need the fundamental building block, which is carbon."
Whether or not life originated on Mars "verges more on philosophy, really," he said. "We don't know how life originated on Earth. I'm really focused on the question, not if life evolved, but if it did evolve where would it be preserved? And where are the places we need to go to find the best potential records of things that could be clues that would lead us on future missions toward the discovery of biosignatures?"
Another instrument, called CheMin, uses X-ray diffraction to identify the minerals in collected rocks and soils. The Mars Hands Lens Imager, mounted on the robot arm, will take close-up photos of selected samples while the Alpha Particle X-ray Spectrometer, also on the arm, measures the abundances of various elements.
A camera mounted on a mast atop the rover will take high-resolution stereo pictures as well as high-definition video. Another mast-mounted instrument known as ChemCam will use a laser to vaporize the surface layers of nearby rocks, a spectrometer to measure the types of materials present in the debris and a camera to photograph the site.
A Radiation Assessment Detector will will characterize the radiation environment at the surface, a key factor in planning for eventual crewed missions, while a suite of Spanish instruments called the Rover Environmental Monitoring Station monitors the martian weather.
An instrument provided by Russia, the Dynamic Albedo of Neutrons experiment, will look for signs of water or ice below the surface.
"We've got this feeling now of Mars as a much more dynamic planet," Grotzinger said. "The thing about this mission is, it's really going to confront the whole problem of the origin of sedimentary rocks on Mars and what they mean. Sedimentary rocks on Earth, they are the overwhelming storehouse of organic materials in the history of life. If you want to explore for those organic materials, you've got to know how these damn rocks formed."
Climbing Mount Sharp may help answer that question, and undoubtedly raise many more, including what to do next.
"There are two major decision points for the science team in this mission," Grotzinger said. "We've done one, which was to pick Gale over the other three landing sites. ... The second big decision is going to be when we get up to a boundary (on Mount Sharp) where you can see that the hydrated minerals go away.
"There are some people who are going to want to go to the top. And there are other people who are going to say, why don't we just go across that boundary and do a bunch of work on the other side, maybe spend a year doing that, and then let's go down again and work on the wet kind of rock types that we saw on the way up.
"I think the team will divide into two groups on that one. That will be a major decision."
CBS News
In a $2.5 billion gamble, a nuclear-powered Mars rover the size of a small car will attempt a pinpoint landing near the base of a 3-mile-high mountain overnight Sunday to search for the building blocks of life and evidence of past or present habitability.
In so doing, the Mars Science Laboratory rover, dubbed "Curiosity" in a student naming contest, will climb layer by layer through vast eras of the red planet's enigmatic history, possibly shedding light on the transition from a warmer, wetter past to the drier, frigid world of more modern epochs.
 |
| The Mars Science Laboratory rover "Curiosity," the centerpiece of a $2.5 billion mission, looks for carbon compounds and signs of past or present habitable environments in the rocks and soil of Gale Crater. (Credit: NASA) |
Doug McCuistion, director of Mars exploration at NASA Headquarters in Washington, said the mission "could arguably be the most important event in the history of planetary exploration."
"It truly is a major step forward, both in technology and in potential science return and science capability to unlock the mysteries of Mars in places that have never been accessible to humankind in the past."
But getting there will not be easy.
The Mars Science Laboratory spacecraft must first endure entry temperatures of up to 3,800 degrees Fahrenheit, crushing deceleration of up to 15 Gs and the 65,000-pound jerk of a huge parachute inflating at supersonic velocity.
After slowing the spacecraft to a bit less than 200 mph, the parachute will be cut away and a rocket-powered descent stage, carrying the Curiosity rover bolted to its belly, will fall free for a nail-biting one-mile plunge to the surface.
Controlled by the rover's main computer, the descent stage will slow to just 1.7 mph, four of its eight rocket engines will shut down and Curiosity will be lowered on the end of a 25-foot-long tether like a bobber on a fishing line.
With the descent stage maintaining its slow fall, the rover's six wheels are expected to touch down on the floor of Gale Crater around 1:17 a.m EDT (GMT-4). Confirmation will be relayed back to Earth in near realtime by NASA's Mars Odyssey satellite.
But because of the distance between Earth and Mars -- about 154 million miles -- it will take 13.8 minutes for confirmation of a successful landing to reach anxious engineers and scientists at NASA's Jet Propulsion Laboratory in Pasadena, Calif. That translates into 1:31 a.m. on Aug. 6, Earth-received time.
"MSL holds the potential to look for evidence of habitable environments, if they existed, on Mars in the distant past," said NASA science chief John Grunsfeld, a veteran shuttle spacewalker. "The Curiosity rover has the potential to discover the building blocks of life on Mars, if life ever existed on Mars.
"However, the Curiosity landing is the hardest NASA robotic mission ever attempted in the history of exploration of Mars or any of our robotic exploration. This is risky business."
Curiosity's novel "sky crane" landing technique has dominated news coverage, in part because it seems so outlandish compared to past missions and because it appears riskier given a full-up, end-to-end test was not possible in Earth's atmosphere and gravity.
But engineers are confident the entry, descent and landing system will work as advertised, the first act in the most complex, expensive and scientifically significant robotic Mars mission ever attempted.
"This rover, the Curiosity rover, is really a rover on steroids," Colleen Hartman, a senior NASA manager, said before launch. "It's an order of magnitude more capable than anything we have ever launched to any planet in the solar system. It will go longer, it will discover more than we can possibly imagine."
Over the course of a planned two-year mission, Curiosity will act as a robotic geologist, using high definition cameras to photograph its surroundings in exquisite detail, beaming back wide-angle high-resolution panoramas as well as close-up microscopic views through what amounts to a geologist's hand lens.
Equipped with 10 state-of-the-art instruments and a sophisticated robot arm, the rover will drill into rocks and soil, use a rock-vaporizing laser to assess more distant targets and collect rock and soil samples for detailed chemical analysis.
 |
| The landing target on the floor of Gale Crater will leave the Curiosity rover near the base of a 3-mile-high mountain of layered terrain. During the course of a planned two-year mission, Curiosity will climb up Mount Sharp, moving from a warmer, wetter past to a colder, drier eras. (Credit: NASA) |
The initial phases of the mission will be focused on the crater floor and an alluvial fan visible from orbit where scientists believe water may have pooled in the distant past.
But the long-range objective is Aeolis Mons, dubbed Mount Sharp by NASA, a huge wind-eroded mound of sedimentary rocks in the center of Gale Crater that rises more than three miles, higher than Mt. Rainier above Seattle.
The instruments aboard Curiosity were not designed to look for signs of life. Rather, the primary goal of the Mars Science Laboratory is to search for carbon compounds and evidence of past or present habitability.
"We are not a life detection mission," Grotzinger said. "The first and important step toward that is to try to understand where the good stuff may be."
Grotzinger would not give odds on finding carbon compounds in Gale Crater, but "the information from orbit looks so darn good ... I'd be surprised if we landed on the surface and didn't find something that looked like it could have been a formerly habitable environment.
"But if you're trying to get me to say what are the chances of finding organic carbon, I'd say it's like looking for a needle in a haystack, and the haystack is as big as a football field."
Searching for carbon compounds is only part of Curiosity's mandate. As it works its way up the 15-degree slopes of Mount Sharp and passes from older to younger layers, the rover is expected to cross over beds marking a geologically sudden transition from a warmer, wetter past to a drier, less hospitable age.
In so doing, hundreds of thousands to tens of millions of years of the planet's evolution will be brought into focus.
"The really cool thing about the Gale stratigraphic succession to me is it's a tour through nearly the entire history of Mars where we can begin to understand these major changes in the environmental history of the planet," Grotzinger said in a more recent interview. "And I can't think of another place on Mars where you can go do that."
To get a sense of the landing site's potential, Grotzinger said the layers making up Mount Sharp are three times thicker than those in the Grand Canyon, which "takes you ... through 300 million years of Earth history, from the origin of animals to the origin of dinosaurs."
"If you were to have remote sensing data from an orbiter around Earth, looking at Earth and the Grand Canyon 150 years ago, nobody would have ever predicted that that's what you would discover if you went there one day," Grotzinger said. "I don't know what it is that we're going to discover about Mars. But I have to believe it's going to be something really good."
The high-stakes mission comes at a critical time for NASA's planetary exploration program as budget pressures threaten to sharply reduce the scope of the agency's robotic missions.
The Obama administration's fiscal 2013 budget request calls for $17.7 billion for NASA, but it cuts $300 million from planetary science, most of it from the Mars program.
 |
| The Curiosity rover, right, dwarfs its predecessors in this photo showing a Mars Exploration Rover on the left and the diminutive Mars Pathfinder. (Credit: NASA) |
As a result, NASA has backed out of a 2008 agreement with the European Space Agency to share the costs of two ambitious Mars missions known as ExoMars, which called for launch of an orbiter in 2016 and two rovers in 2018.
Along with searching for signs of past or present life on Mars, the missions also would have tested technologies needed for a long-sought sample return mission.
"Tough choices had to be made," NASA Administrator Charlie Bolden said when the budget was unveiled earlier this year. "This means we will not be moving forward with the planned 2016 and 2018 ExoMars mission. ... Instead, we'll develop an integrated strategy to ensure the next steps in Mars exploration will support science as well as human exploration goals and potentially take advantage of the 2018 and 2020 exploration windows."
In the wake of the budget's release, Bill Nye, chairman of the Planetary Society, said the "priorities reflected in this budget would take us down the wrong path."
"Science is the part of NASA that's actually conducting interesting and scientifically important missions," he said in a statement. "Spacecraft sent to Mars, Saturn, Mercury, the Moon, comets and asteroids have been making incredible discoveries, with more to come from recent launches to Jupiter, the Moon and Mars. The country needs more of these robotic space exploration missions, not less."
In a rare show of bipartisan agreement, Rep. Adam Schiff, D-Calif., and John Culberson, R-Texas, whose states include NASA field centers, wrote in Space News that without congressional action, "the administration's cuts to planetary science would devastate America's planetary program."
"The robotic Mars program, one of our nation’s science jewels, faces the most severe cuts, including a rover mission to Mars in 2018 identified as the highest priority in planetary science in the most recent decadal survey," they wrote. "This would be a tragic loss for a program that has made major scientific discoveries and captured the interest of people around the world."
The Curiosity rover is the only so-called "flagship" mission currently in the Mars pipeline and it takes years to plan, design and build new spacecraft. Aerospace engineer Robert Zubrin, president of the Mars Society and author of "The Case for Mars," said in an interview that the fate of NASA's Mars program rests firmly on Curiosity's shoulders.
"This is a superb mission, if it succeeds," he said. "On the other hand, if it fails, it's the flagship out the window. That would be serious enough. But the stakes were upped this past February when the Obama administration canceled the 2016 and 2018 missions, and thus completely scrambled the program, completely set it adrift."
If Curiosity fails, he said, "not only do you lose this mission, but I think we lose the rest of the decade. On the other hand, if this succeeds, it will be a brilliant mission, it will be the best Mars mission ever flown and I think we have a real chance of not only reversing the missions that were cut but moving on towards sample return."
MSL Project Manager Pete Theisinger said in an interview that he was aware of the outside scrutiny and pressure to chalk up a success. But he said the MSL team was not distracted.
"Down in the trenches where the work's actually accomplished, people love what they do, they're very professional about it and they want to do the right job and so that's all they think about," he said. "It wouldn't matter whether it was this two-and-a-half-billion-dollar thing that's on the national stage or it was a $100,000 thing in the lab. They feel the same.
"When you get up to the top of the food chain, yeah, there's a feeling that this is a very visible mission, we know that, people like you don't call me if it's not a very visible mission. And so, we know that. But once again, the job is to get the job done and to do it in the best balanced, prudent approach that we can. I don't think we feel it, we just know it's there."
 |
| The Mars Science Laboratory mission gets underway Nov. 23, 2011, with launch atop a United Launch Alliance Atlas 5 rocket at the Cape Canaveral Air Force Station. (Credit: Justin Ray/Spaceflight Now) |
Launch originally was planned for 2009, but in 2008, the flight was delayed two years to verify the integrity of the myriad actuators used in the rover's mobility system and robot arm, a delay that added $400 million to the project's price tag.
Curiosity's journey finally got underway on Nov. 26, 2011, when a United Launch Alliance Atlas 5 rocket boosted the craft into space. The spacecraft has performed in near flawless fashion during the long cruise to Mars and now the stage is set for entry, descent and landing Aug. 6.
Acting as a robotic geologist, Curiosity is well suited for its trailblazing mission, dwarfing the hugely successful Spirit and Opportunity rovers both in size and scientific capability. The instruments carried by each of the earlier rovers weighed about 11 pounds. The 10 aboard Curiosity weigh 165 pounds.
Not counting its robot arm, Curiosity is 10 feet long, nine feet wide and seven feet high measured to the top of its main camera mast. Its mobility system is similar in design to that used by Spirit and Opportunity, but its six 20-inch-wide wheels are twice the size of the earlier models. Each wheel has its own drive motor and the four corner wheels are independently steerable.
Top speed is over hard, flat ground is about a tenth of a foot per second, although the rover typically will move at half that velocity when operating autonomously and using hazard avoidance.
The earlier rovers were solar powered, forcing them to shut down at night and to hibernate in winter months to conserve power and heat. MSL is powered by a radioisotope thermoelectric generator, using the heat produced by the decay of radioactive plutonium dioxide to generate electricity. Excess heat is used to keep electronics and other sensitive systems from getting too cold.
Curiosity is equipped with redundant computers, using one at a time and keeping the other as a backup. The computers feature radiation-resistant PowerPC 750 processors operating at 200 megahertz with two gigabytes of flash memory storage, about eight times more than Spirit and Opportunity.
The system was designed from the ground up to use the orbiting Odyssey and Mars Reconnaissance Orbiter satellites to relay engineering and scientific data back to Earth.
Independent of the weather and the sun, Curiosity is designed to operate for at least one martian year -- two Earth years -- and to rove at least 12 miles. But engineers expect it to continue operating well beyond its design specification, both in time and distance.
"You're asking a project manager how long it's supposed to live and you expect an answer?" Theisinger laughed. "We test these things, the mechanical or moving parts, we test for either two or three times life, usually three times life. So if we know a wheel is supposed to run for 20 kilometers, we'll test it to 60 kilometers.
"We don't test them to failure. All that we know is that we've tested the mechanisms for two or three times life and they all passed that test program. The RTG is good for a decade, 12 years, 15 years, something like that, before we really get into power issues. The battery is probably good for eight years. The electronics are high reliability electronics, but some of it is single string.
"It could last a long time if we haven't made a mistake," he said. "If Mars doesn't get us, it could last a long time."
The heart of the spacecraft is the most sophisticated instrument package ever sent to Mars.
 |
| The Curiosity rover, on the move in Gale Crater. (Credit: NASA) |
The Sample Analysis at Mars, or SAM, instruments will be used to analyze soil and rock fragments delivered by the lander's robot arm. It includes a gas chromatograph, a mass spectrometer and a laser spectrometer to look for carbon compounds and measure isotope ratios, which will shed light on the history and distribution of water and the evolution of the martian atmosphere.
"You've got to have water for life as we know it," Grotzinger told CNET in an earlier interview. "The second thing is you need a source of energy. ... And then the important thing is, you need the fundamental building block, which is carbon."
Whether or not life originated on Mars "verges more on philosophy, really," he said. "We don't know how life originated on Earth. I'm really focused on the question, not if life evolved, but if it did evolve where would it be preserved? And where are the places we need to go to find the best potential records of things that could be clues that would lead us on future missions toward the discovery of biosignatures?"
Another instrument, called CheMin, uses X-ray diffraction to identify the minerals in collected rocks and soils. The Mars Hands Lens Imager, mounted on the robot arm, will take close-up photos of selected samples while the Alpha Particle X-ray Spectrometer, also on the arm, measures the abundances of various elements.
A camera mounted on a mast atop the rover will take high-resolution stereo pictures as well as high-definition video. Another mast-mounted instrument known as ChemCam will use a laser to vaporize the surface layers of nearby rocks, a spectrometer to measure the types of materials present in the debris and a camera to photograph the site.
A Radiation Assessment Detector will will characterize the radiation environment at the surface, a key factor in planning for eventual crewed missions, while a suite of Spanish instruments called the Rover Environmental Monitoring Station monitors the martian weather.
An instrument provided by Russia, the Dynamic Albedo of Neutrons experiment, will look for signs of water or ice below the surface.
"We've got this feeling now of Mars as a much more dynamic planet," Grotzinger said. "The thing about this mission is, it's really going to confront the whole problem of the origin of sedimentary rocks on Mars and what they mean. Sedimentary rocks on Earth, they are the overwhelming storehouse of organic materials in the history of life. If you want to explore for those organic materials, you've got to know how these damn rocks formed."
Climbing Mount Sharp may help answer that question, and undoubtedly raise many more, including what to do next.
"There are two major decision points for the science team in this mission," Grotzinger said. "We've done one, which was to pick Gale over the other three landing sites. ... The second big decision is going to be when we get up to a boundary (on Mount Sharp) where you can see that the hydrated minerals go away.
"There are some people who are going to want to go to the top. And there are other people who are going to say, why don't we just go across that boundary and do a bunch of work on the other side, maybe spend a year doing that, and then let's go down again and work on the wet kind of rock types that we saw on the way up.
"I think the team will divide into two groups on that one. That will be a major decision."