Mars has been both a wonder and mystery all throughout human history. To our ancestors, it was one of the few points of light in the sky that moved with regularity--and the only one with a distinctive reddish glare. When philosophers and scientists looked up at the heavens and began wondering about the possibility of other worlds, Mars was the first to be populated by fantastic creatures of our imaginations. From nubile princess in jeweled towers to maleovelent tentacled invaders in tripod machines, Mars has been home to some of our most fertile and wildest flights of fantasy.
In the modern era of space flight, we of course learned that Mars is actually a cold, lifeless, alien desert with an unbreathable atmosphere. Yet it still tugs powerfully at the popular imagination, and has become on of the major focal points of our exploration of space. Of all the even more hostile worlds in the Solar System, it is the one most like Earth. Some believe it may even, centuries hence, become humanityís second great home in the cosmos.
Mars has been visited by a veritable fleet of spacecraft since the 1960s. The Mariner flyby probes were the first to photograph its surface from space, and numerous orbiters, landers, and rovers have explored it since.
It is not all a great success atory, however. Many spacecraft have been lost in the vicinity of Mars, and only 5 of the 15 attempts to land on Mars have been successful. This is an indication of how difficult interplanetary flight can be. Though people talk of a Mars "curse", the truth is Mars missions have suffered the most mishaps because it is the destination most interplanetary spacecraft have been sent to. Its almost a certainty that a similar failure rate would have been accrued had the same number of probes been sent to other planets as well.
This is not to say that things will always be this way. Technology and techniques for interplanetary flight are improving all the time. Smarter, tougher, and more capable probes are being designed and built even as these words are read. Survival rate of Mars-bound craft is sure to improve in the future, and as such our knowledge of this intriguing planet will increase that much more.
To understand what scientists hope to learn from studying Mars, and to get an insight into why their spacecraft and probes are designed the way they are, one should review Mars and its physical characeristics. Links to more information on Mars can be fund in the "Further Information" section at the end of this article.
This article discusses mission either underway or at some point in the planning stages. Manned missions to Mars, still just speculation, will be adressed in another article.
Launched in August of 2007 and expected to reach the Mars in May of 2008, this NASA lander in intended to touch down in the extreme northern lattitudes of the planet and probe the mysteries of the ice buried just inches beneath the martian soil. The lander with carry a robotic arm that will be capable of digging up to half a meter into the ground, and a sophisticated on-board automated laboratory for analyzing the samples obtained.
When the launch window to Mars opens up again in fall 2009, NASA will launch the Mars Science Observatory. Reaching Mars nearly a year later, this large rover is three times the size of the Spirit and Opportunity rovers and will contain sophisticated scientific instruments built by Russia, Spain, and Canada. Like the Pheonix lander before it, it will have a robotic arm for collecting soil samples and an onboard laboratory for analyzing them. Powered by a radioisotope system, the rover is expected to have an operational life span of at least a full Martian year (almost two Earth years) while allowing for far greater maneuverability and speed than the previous rovers.
Also being considered for the 2009 Launch window is an orbiter carrying an advanced aperture radar array that would more accurately map Mars then ever before. This sphpisticated radar will also be able to penetrate many meters below the ground to reveals structures we may not yet be aware of, such as the extent and thickness of the suspected planet-wide subsurface permafrost layer. The mission is being developed as a joint venture between NASA and the Italian Space Agency.
CNES (the French Space Agency) had planned to launch a remote sensing orbiter and four small "Netlanders" in 2007 but these have been postponed indefinitely. However, this project may yet be resurrected if budget issues are resolved.
A great many proposals have been fielded by NASA in recent years concerning missions to Mars, but few have generated as much potential exceitement as a sample return mission.
Such a mission would consist of a rugged lander, similar to the current Pheonix platform but larger, than would touch down on Mars. Usinge robotic arms to dig into the soil and collect samples, it would then load up its prizes into a small ascent vehicle located on the lander. This powerful miniature rocket mates with an orbiter above Mars, which then breaks orbit and coasts back to Earth. Many months later, the returning spacecraft is either rendezvoused in orbit by a manned craft to retrieve the samples, or the samples are loaded into a small drop capsule for a return to Earth.
Such a sample return mission would at most return a few pounds of soil and rocks to Earth, and would test our currently capabilities in designing and utilizing robotic probes at interplanetary distances. It would in fact be the most complex and challenging interplanetary mission carried out to date.
Some visions of the mission include the use of small Sojourner-like rovers to gather the samples from optimal locations around the lander, and the need for self-welding seals to ensure that the samples will in no way be contaminated by Earthís environment upon its return.
A bit of controversy surrounded the mission as it had to be pushed back a number of years because of the "refocusing" of the space program following the 2004 announcement of a return to the Moon. However, NASA still plans on moving forward with a sample return mission, now tentatively planned to be launched sometime between 2014 and 2020.
Also of interest in future missions are surface-penetration technologies, where probes could dig deep beneath the surface in order to search for the chemical clues to water and possible life on the Red Planet. Three general methods for exploraing beneath the surface are being considered.
The first is with a deep-penetrator deadfall probe. Basically this is a small, hardened, elongated vehicle that dropped onto the surface from high altitude--possibly even orbit--and uses the sheer force of its plummet to slam into the ground up to several meters. The back end of the probe ideally would remain above the surface and contain radio equipment that would maintain cotact with the mother craft in orbit.
The second is to have a fairly large lander touch down on the surface with long, extendable drill. However, drilling deeply on Mars present a number of difficulties, such as how the material dug up can be removed from the bore hole (one Earth thatís usually done by water, something in short supply on the Martian surface), and how to keep deep bore hole from collapsing. The latter on Earth is usually done with hevay stel plating, something thatwould be quite expensive and difficult to drag all the way to the fourth planet.
A third alternative is to use a robotic mole. This is basically a small robot that pulverizes rock and soil as it goes, avoiding the need for a complex drilling apparatus. A small flexible tube will connect it with its lander, in order to monitor its operation and allow for data transfer. A small experimental robot mole, meant to only penetrate about a meter downward, was carried aboard the 2003 ESA lander mission Beagle, but unfortunately that probe was lost upon its descent to the Martian surface.
Another idea discussed often for future missions is the use of specially designed aircraft that could fly about the landscape gathering data about Martian weather, conditions, and atmospheric chemistry.
Miniaturized airplanes have been considered, but the conditions on Mars--especially its very thin atmosphere--would make take-off very difficult from the ground. It would need a very large wingspan, but that is something that may be easier on Mars to achieve thanks to its lighter gravity. It would be constructed similar to the way many ultra-light air vehicles are made on Earth, with a sparse framework made from advanced composite materials, low-power but highly efficient motors, and perhaps even its whole topside convered with lightweight solar panels for extra energy.
Instead of launching it from a downed lander, an airplane could be released from a probe just as its beginning to make its descent into the lower atmosphere. Once released, it would slowly spiral to the ground, its flight perhaps lasting a mere hour or two. Still, an airplane probe could be invaluable for gathering images and data on areas very hard to reach via lander or rover, such as rift valleys, mountains, and deep craters.
Balloons may also be used by future robotic explorers. In a way, this is already a proven technology--balloons have been deployed for decades in Earthís stratosphere, which resembles the Martian atmosphere in density. A balloon would be carried to the surface by a lander, which would then inflate it via on-board helium tanks. The balloon would then drift up and away carrying an instrument package. Such a balloon, if it reached sufficient altitude, could remain aloft for months at a time.
A special type of balloon being considered for use on Mars is a solar Montgolfiere, named after the French brothers who flew the first hot air balloon. The Montgolfiere would be released during descent into the atmosphere, where its fall would fill it full of Martian air. The heat from sunight expands the air, keeping the balloon aloft. The Montgoflier could stay aloft only as long as the sun was out, but it would also save a great deal of weight by not needing large, heavy cannisters to inflate it.
Balloons can provide soft landing for small payloads into potentially hazardous terrain, as well as providing high-altitude imaging and reconnaissance.
Information On Mars: