Scientists and engineers are working on machines to do the most difficult jobs in space. Here we present some of the impressive space robots that may soon rewrite our understanding of much of our solar system.
Since 1995 astronomers have discovered some 550 confirmed planets orbiting other stars. NASA's Kepler space telescope is in the process of uncovering thousands more, including ones similar to Earth in size and temperature. Before long, people will be clamoring to know what they look like. The only way to find out is to go there. But reaching even the nearest star system, Alpha Centauri, within a human lifetime would require a spacecraft capable of cruising at 10,000 miles a second. Voyager 1, the fastest-moving spacecraft, is moving at one-tenth of 1 percent of that speed.
Although NASA canceled its Breakthrough Propulsion Physics project in 2002, engineers are still pushing the limits of speed and range. The New Horizons probe has the most distant target of any space mission ever attempted: everyone's favorite dwarf planet, Pluto, which it will reach in July 2015. Around the same time, scientists will begin testing a prototype of the Variable Specific Impulse Magnetoplasma Rocket, or VASIMR, which expels searing hot plasma to produce thrust, at the International Space Station. VASIMR will not reach the stars, but it may allow future probes to leave the solar system in years rather than decades. True star travel will probably require technologies like antimatter or nuclear fusion rockets, which are currently not much more than dreams.
Almost every probe ever sent into space has been equipped to detect oxygen, liquid water, and organic chemicals--key signs of the potential for life. But unless a large, preferably green alien walks past the camera of an unsuspecting rover, actually finding a pulse out in space will be a difficult proposition. Piloting a robot from millions of miles away is hard enough to begin with. And even if the robot detects an intriguing chemical, how do you tell whether the molecules came from a microbe or from complex but nonbiological chemistry? Right now, you don't.
NASA's current best hope in the E.T. hunt is Curiosity, a $2 billion Mars rover that launches later this year. Curiosity's ChemCam will fire a laser at rocks up to 30 feet away and analyze the color of the vaporizing mass to determine its chemical composition. Should the ChemCam identify an interesting sample, the whole rover can move in for a closer look, clutching samples with a robotic arm and using a battery of sensors to catalog the chemicals inside them. Looking farther ahead, a team at MIT and Massachusetts General Hospital-Harvard is designing an instrument that will be able to scan for alien DNA and RNA. "This experiment would be the first to look for life by targeting the molecules specific to life as we know it," says Christopher Carr, the lead engineer on the project. If a probe finds something to sequence, that would be almost definitive proof that life took hold on Mars and very likely is thriving there right now. Carr hopes his device will fly on a NASA Mars mission within the next decade.
Setting a massive drill loose on the moon or Mars would be ideal for extracting deep rocks for scientific analysis and extraterrestrial prospecting. Problem is, drilling is hard on Earth and even harder off it. The moon has only one-sixth Earth's gravity, so a lunar drilling system needs six times as much mass to exert the same force as it would here--a grim reality when each additional pound of payload can add millions of dollars to the cost of a rocket. Complicating matters, a space drill must operate efficiently and virtually autonomously since sending humans to make repairs or resupply fuel would not be feasible.
With those concerns in mind, New York City-based Honeybee Robotics is reimagining the drill for space exploration. Instead of forcefully grinding with a sharp drill bit, Honeybee's drills use a more energy-efficient hammering motion with blunt bits to fracture the bedrock. In December the company's prototype Mars drill, IceBreaker, autonomously drilled a one-meter hole into an Antarctic glacier within an hour using far less energy than it takes to brew a pot of coffee. Honeybee is already gearing up to drill on the moon. As early as 2013 a privately launched rover equipped with the company's MoonBreaker drill will hammer a half meter into the lunar surface and collect samples for analysis by the rover's instruments.
The best scientific payoffs require venturing to the harshest environments, where blistering volcanoes or subarctic icescapes could instantly transform multimillion-dollar machines into scrap metal.
One bold proposal comes from a team led by planetary geologist Ellen Stofan at the technical consulting firm Proxemy Research. The Titan Mare Explorer, or TiME, is a 500-pound robot that would take to the seas of Saturn's giant moon Titan, the only solar system body other than Earth that has liquid on its surface. The probe, powered by a newly developed battery made of plutonium, would have a protective outer shell to shield it while it bobs along in a -300 degree F lake of liquid natural gas. Titan's gentle winds will push TiME along as it snaps photos and measures the moon's rich mix of organic compounds. "A lot of the chemistry on early Earth involved the same chemicals, but Titan has them in a deep freeze," Stofan says.
NASA will decide TiME's fate next year. Meanwhile, the agency is mulling missions to the slope of a volcano on Venus and an ocean miles beneath the icy surface of Jupiter's moon Europa.
If we cannot get people to Mars, the next best option is to bring Mars to us. A few rocks delivered to labs on Earth could lead to a drastically deeper understanding of the Red Planet's geology, its potential to support life, and its suitability as a target for future astronauts. "I'm convinced that a robotic sample return is the single biggest step that we as planetary scientists could take to foster human exploration of Mars," says planetary scientist and former NASA associate administrator Alan Stern.
The National Research Council agrees. In March the nonprofit advisory group recommended making sample return one of NASA's top priorities for planetary science. NASA plans to hone its sample-return skills in 2016 with OSIRIS-REx, a boxy spacecraft that will land on an asteroid, collect chunks of rock and dust, and then return to Earth.
By 2018 NASA and the European Space Agency hope to launch the first phase of bringing back Mars samples. Cost concerns have kept the details of the mission in flux, but at its most basic, it will probably entail a rover to collect samples, an ascent vehicle to carry the payload into orbit around Mars, and a spacecraft to carry the precious cargo home.
This gallery is adapted from DISCOVER's September 2011 issue.