But, unlike cars on Earth, the rover doesn't drive on smooth, paved roads. The rover moves on rocky and sandy martian terrain. The rover wheels might have a hard time grasping onto the loose-gravel ground. The wheels could spin in place before they actually gain tracking. So if the wheels spin four times before they find firm footing, the odometer will read centimeters, and the rover will stop.
Thus, the rover will believe it has moved forward centimeters, when in reality, it hasn't moved at all and may have dug itself into a rut instead. Without other safety checks it might then turn and bang its wide solar panel wing into a rock behind it that wouldn't have been in the area if the rover had moved forward.
The rover would then continue to follow the chain of commands and extend its robotic arm, hoping to meet the rock centimeters from where the rover began its "trek. Imagine yourself being given a command to walk from your bedroom to your kitchen, and the only way to get there was to follow these rules:. Now imagine how much easier it would be to get from your bedroom to your kitchen if you could open your eyes every 30 centimeters 1 foot to reassess the situation.
With the hazard avoidance software, the rover can travel safely an average of 30 centimeters 1 foot. How much does it see? The rover uses pairs of Hazcam images to map out the shape of the terrain as far as 3 meters 10 feet in front of it, in a "wedge" shape that is over 4 meters wide at the farthest distance. It needs to see far to either side because unlike human eyes, the Hazcam cameras cannot move independently; they're mounted directly to the rover body. Who chooses where it should go?
Using visuals previously downlinked from the Navcams, the scientists and engineers give the rover a "go to waypoint" command, which includes the distance and heading of the intended destination. Later commands give the locations of the targets where the rover should deploy the science instruments. So people tell it what its goal is, but the rover chooses the best way to get there. The "go to waypoint" command also contains a coordinate "boundary" of acceptable distance from the target.
This boundary gives the flight team a high level of confidence that the rover will avoid driving on or over the target or into dangerous terrain that was out of the line of sight from the Navcams, and also prevents the rover from spending too much time getting to an "exact" location, since it might have slipped a little anyway.
The "go to waypoint" command includes time and distance limits that protect both against missing the target and also against being diverted too far from the goal by obstacles. For example, if the target is 60 centimeters 2 feet away on flat surface, and the rover is still moving after 2 minutes 1 minute longer than the trip should have taken , something most likely is wrong and the rover will stop. Fixed time limits are also given to the rover wheels for each "step" that the rover takes when going to a waypoint.
If the rover were to get stuck on a single step, this limit would prevent it from running the wheel motors until the overall timeout for the "go to waypoint" command expired which could potentially be very long, perhaps tens of minutes to hours for far field traverses. And the technology doesn't disappoint; the rover Curiosity , launched in , has instruments on it that truly belong in a science fiction movie.
Hint: lasers. So far, there have been more than 40 attempts to make contact with Mars. The first five missions took place from to , by the former USSR. All the missions were flybys of the planet, meaning that vessels were launched into Mars' orbit to send back images.
Those missions were all failures; either the spacecraft didn't make it to the planet or the spacecraft broke apart during the trip.
The first successful mission was the trip by the Mariner 4, a United States craft that returned 21 images of the planet. In the following pages, we'll explore not just the rovers themselves but also some of the discoveries they made. Let's roll to the next page to see why, exactly, we're sending rovers in the first place. So if we're so advanced and fancy that we can build extremely complicated robots to Mars , why can't we just send Terry the Astronaut?
The most important reason is also probably the most obvious: Terry probably just wouldn't make it there. That is, only about a third of the missions launched thus far have been "successful," meaning that they've made a trip to Mars intact. While it's easy to be optimistic about the nearly one-third of rovers that have provided us with valuable information, it's not as easy to cheerlead a track record like that when Terry the Astronaut is in the picture. Few of us enjoy the odds of dying every three days at work.
Cost, of course, is another factor. Or return from Mars, for that matter. Keep in mind that the rovers get to stay on Mars forever when we're done with them, but Terry the Astronaut's trip is more a vacation than a move. And that means food, fuel, waste disposal and a plethora of other costs -- twice. Beyond logistics and cost are all the vast unknowns about how the human system could react to an atmosphere like Mars. Because Mars has no magnetic field , humans would receive whopping doses of cosmic radiation -- not a problem on Earth, where the planet's magnetic field works to block it out.
A 1,day trip to Mars has the potential to result in a 40 percent chance of the astronaut developing cancer after returning to Earth -- not necessarily something a lot of people are looking for when interviewing for a job [source: NASA Science ]. Keep in mind, too, that if Terry the Astronaut is also Terry the Woman, she's at even more risk: Having breasts and female reproductive organs present nearly double the risk for cancer [source: NASA Science ].
So without Terry the Astronaut signing up for massive doses of cancer-causing rays, we're left with robotic explorers. Jet over to the next page to learn about some of the missions to Mars. The most enticing thing about Mars exploration is the promise of finding water -- or past evidence of water.
The first missions to Mars were flybys ; that means they were simply orbiting vessels that sent back photographs of the planet. The first one was Mariner 3 in ; however, the first successful orbit and photographs came in from Mariner 4.
When the flybys ended in , the next series of missions were referred to as orbiters. NASA designed these spacecraft for longer-term orbiting around Mars, collecting photographs. Mariner 9, in , was the first to take photographs of the entire surface of Mars. Orbiting missions have continued, including the launch of the Mars Reconnaissance Orbiter. The orbiter could spot objects as small as a dinner plate, while also carrying sounders to find subsurface water. Perhaps most important, it's still used as a crucial communications tool for relaying information back to mission control.
But let's wander over to the rovers' predecessors now. Viking 1 and 2, which launched in the mid-'70s, both had landers that descended to the surface of Mars. They were the first to discover that Mars was self-sterilizing, meaning that the combination of ultraviolet radiation with the dry soil and oxidizing nature of the soil chemistry prevents organisms from forming. When we think of more modern machines landing on Mars, we usually start with the Pathfinder mission.
The Pathfinder consisted of a lander, equipped with a parachute for entering Mars' atmosphere, and the Sojourner rover. The equipment returned thousands of images, as well as 15 chemical analyses of soil and weather data. In , the Mars Exploration Rover mission team launched Spirit and Opportunity, one of which was still traversing the planet as ended. Let's crawl over to the next page to learn more about those rovers, their technology and discoveries.
Spirit and Opportunity, it turns out, aren't just words we use to make ourselves feel better when we're depressed. In , NASA launched the cheerfully named Spirit and Opportunity rovers, which embarked on a mission of far greater mobility and distance than Pathfinder. Both the rovers share a few noteworthy features.
They can both generate power from solar panels and store it in internal batteries. Just in case any little green men are nearby, the rovers can take high-resolution color images or bust out magnifying cameras for Earthbound scientists to scrutinize objects. Multiple spectrometers on the arm of the rovers employ all sorts of tricks to determine the composition of rocks, including tracking how much heat an object is giving off and firing alpha particles at it.
One study described the discovery of more organic molecules in 3. The seasonal changes could mean that the gas is produced from living organisms, but there's no definitive proof of that yet. Besides hunting for habitability, Curiosity has other instruments on board that are designed to learn more about the environment surrounding it. Among those goals is to have a continuous record of weather and radiation observations to determine how suitable the site would be for an eventual human mission.
Curiosity's Radiation Assessment Detector runs for 15 minutes every hour to measure a swath of radiation on the ground and in the atmosphere. Scientists in particular are interested in measuring "secondary rays" or radiation that can generate lower-energy particles after it hits the gas molecules in the atmosphere. Gamma-rays or neutrons generated by this process can cause a risk to humans. Additionally, an ultraviolet sensor stuck on Curiosity's deck tracks radiation continuously.
A mission with days flying to Mars, days on the surface and days heading back to Earth would create a dose of 1. The total lifetime limit for European Space Agency astronauts is 1 sievert, which is associated with a 5-percent increase in fatal cancer risk over a person's lifetime.
The Rover Environmental Monitoring Station measures the wind's speed and chart its direction, as well as determining temperature and humidity in the surrounding air. By , scientists were able to see long-term trends in atmospheric pressure and air humidity. Some of these changes occur when the winter carbon-dioxide polar caps melt in the spring, dumping huge amounts of moisture into the air. In early , Curiosity sent back pictures of crystals that could have formed from ancient lakes on Mars.
There are multiple hypotheses for these features, but one possibility is they formed after salts concentrated in an evaporating water lake. Some Internet rumors speculated the features were actually signs of burrowing life , but NASA quickly discounted that hypothesis based on their linear angles — a feature that is very similar to crystalline growth. Vapors from a "wet chemistry" experiment filled with a fluid called MTBSTFA N-methyl-N-tert-butyldimethylsilyl-trifluoroacetamide contaminated a gas-sniffing analysis instrument shortly after Curiosity landed.
Since the scientists knew the collected samples were already reacting with the vapor, they eventually derived a way to seek and preserve the organics after extracting, collecting and analyzing the vapor. Curiosity had a dangerous computer glitch just six months after landing that put the rover within only an hour of losing contact with Earth forever, NASA revealed in Another brief glitch in briefly stopped science work, but the rover quickly resumed its mission.
In the months after landing, NASA noticed damage to the rover's wheels appearing much faster than expected. By , controllers made in the rover's routing to slow down the appearance of dings and holes. It's just the magnitude of what we're seeing that was the surprise. NASA pioneered a new drilling technique at Mount Sharp in February to begin operations at a lower setting, a requirement for working with the soft rock in some of the region.
Previously, a rock sample shattered after being probed with the drill. Engineers had mechanical trouble with Curiosity's drill starting in ate , when a motor linked with two stabilizing posts on the drill bit ceased working.
NASA examined several alternative drilling techniques, and on May 20, the drill obtained its first samples in more than 18 months. It should be noted that Curiosity isn't working alone on the Red Planet.
Accompanying it is a "team" of other spacecraft from several countries, often working collaboratively to achieve science goals. As of mid, Curiosity is working on the surface along with another NASA rover called Opportunity , which has been roaming the surface since Opportunity was initially designed for a day mission, but remains active after more than 14 years on Mars.
It also found past evidence of water while exploring the plains and two large craters. NASA's Mars Odyssey acts as a communications relay for Curiosity and Opportunity, while also performing science of its own — such as searching for water ice. More surface missions are on the way shortly. Mars will carry different instruments, however, to better probe for ancient life.
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