It seemed a lonely existence just to see as far as what we thought was the edge of the universe 100 years ago.
Turns out, it was just the far fringes of the Milky Way.
Now our most powerful orbital telescopes can send us images of galaxies billions of light years from Earth, and though this has inspired hope in astronomers of eventually detecting intelligent life somewhere in the billions of worlds out there, until then our limited technology has left us scraping the surface of a desolate red-coloured planet that on average is around 225 million kilometres (140 million miles) from Earth – a mere eight light minutes. That’s a cosmic heartbeat away that will take the Mars rover Curiosity nine months to reach, and though the odds of mankind discovering life on another planet within our own lifetimes are similarly astronomical, Curiosity is keeping the dream alive. Once it has landed, its job will then be to study Mars for a full Martian year (about 687 Earth days), gathering samples and exploring its surface like no other rover before it, making the most comprehensive assessment yet of whether Mars was ever capable of supporting life.
This is far from the first time NASA, or any other governmental space organisation, has undertaken a mission to investigate our second-closest planetary neighbour in the Solar System. In the last 50 years, four different space agencies have sent 39 various probes, satellites and rovers to the Red Planet.
The first two, Korabl 4 and 5, were Martian probes launched on 10 and 14 October 1960, respectively, by the USSR and both of which were abject failures, unable even to obtain orbit around the Earth. The USSR’s next attempt in 1962, Korabl 11, did achieve Earth orbit but then broke apart. Korabl 13 suffered the same fate as Korabl 11 and the US’s first shot at a Mars flyby with NASA’s Mariner 3 failed to release a heatshield when it entered Earth orbit, the weight of which made it too heavy to achieve a Mars trajectory. Like so much other space junk, the terminated Mariner 3 project is now fated to orbit the Sun forever.
So it took a total of six attempts at getting to Mars before Mariner 4 flew past the planet in 1964 and took 21 photos of the surface in unprecedented detail. Since then 16 missions to Mars have overcome the difficult launch stage and achieved their goal, sending back data that has increased exponentially with our own space exploration technology. Based on the vital information gathered by the first successful soft landing on Mars, Viking 1, NASA’s 1975 Viking 2 craft was able to land in a more advantageous position closer to the Martian north pole, to help take the photos that produced the Martian atlas that’s still used today.
In 1996 the Mars Global Surveyor (MGS) became one of the most successful Mars orbiters ever, taking more images than all other Mars missions put together. And it seems that NASA in particular has been getting much better at the Mars gig recently; since the turn of the millennium, the US space agency has launched five missions to the Red Planet, all of them a resounding success with two that have exceeded their operating lifetime by 15 times the original NASA warranty. The Mars Exploration Rover Spirit was launched in June 2003 and landed in January 2004, moving several kilometres across the surface before it found evidence of water existing some time in the past. Spirit’s success was amplified by the fact that it has hobbled with one stuck wheel for years, a blessing in disguise for NASA as the public warmed to the intrepid vehicle while it dutifully soldiered on despite the odds.
Opportunity was launched a month after Spirit and is still active today, having roved a 33-kilometre (20.5-mile) stretch to a crater called Endeavour that’s 22 kilometres (13.7 miles) in diameter; it is currently exploring this feature. The tenacity of both Spirit and Opportunity bodes well for NASA’s next generation of Mars rover, the Curiosity, which launched on 26 November 2011 and is due to make its landing on 6 August 2012.
Why go to Mars?
The primary reason we’re incessantly firing more and more investigatory craft at Mars than any other planet is, as simple as it sounds, that it’s close to us. Not as close as Venus, but the surface of the second-nearest planet to the Sun has an atmospheric pressure 92 times that of Earth and a 462-degree-Celsius (863-degree-Fahrenheit) temperature that’s hot enough to melt zinc. That was enough to put the Soviet probe Venera 7 out of action within an hour when it landed on Venus in 1970, and enough to put NASA off sending its own lander to be cooked and crushed on the deadly planet until nearly a decade after. By contrast, the thin atmosphere and -140 to 20-degree-Celsius (-220 to 68-degree-Fahrenheit) temperature range on the surface of Mars is far less hostile to our intrepid robots.
Unlike Venus, Mars also exists in the same ‘Goldilocks’ orbital zone as the Earth – that balmy circumstellar habitable region where a planet with the right atmospheric pressure can maintain liquid water on its surface. Moreover, we’ve already discovered evidence for the wet stuff on Mars -and where there’s liquid water, there’s the potential for life.
Journey to the Red Planet
Three months after the successful landing of both Spirit and Opportunity, NASA began research for instruments to be used aboard the Mars Science Laboratory. But exploring and experimenting on Mars was only half the mission; first Curiosity needed to get to Mars. At the size and weight of a small car – five times that of Curiosity’s predecessors – NASA couldn’t simply rely on the old technology to safely deliver the rover.
There were several factors to consider: how to escape Earth’s gravity and set Curiosity on the right trajectory, keeping a steady course, entering Mars’s atmosphere and then safely landing.
First of all, the launch vehicle had to provide the appropriate amount of velocity needed to escape Earth’s gravity. Considering the fully loaded Curiosity weighs in at 900 kilograms (2,000 pounds), NASA chose the tried-and-tested Atlas V 541, a variation on the Atlas V ELV (expendable launch vehicle) family with a near-perfect record since its maiden voyage in 2002. When fuelled with the liquid oxygen and kerosene propellant that makes up half its weight, the Atlas V can provide a whopping 387,500 kilograms-force (854,300 pounds-force) of thrust.
Attached to the Atlas V were four solid rocket motors. These were designed to give the Atlas V the additional boost it required to achieve orbit. Their solid fuel and oxidiser propellant provided this necessary push and, once ignited, burned until their fuel was completely expended before falling back to Earth. Once the Atlas had achieved the right altitude, the brawn of the mission had done its job and it was time for the brains to take over.
The second stage of the launch involved the Centaur, the upper-stage rocket that housed not only a liquid hydrogen and oxygen engine but the Curiosity payload and the flight control computer. The Centaur fired twice with up to 10,100 kilograms-force (22,300 pounds-force) of thrust using the computer to precisely adjust its direction: once to insert itself into low Earth orbit, then once again to launch Curiosity in its spacecraft on its way to Mars with a carefully calculated altitude and rate of spin. Having shed its protective fairing, the active part of the Mars Science Laboratory had gone from a pre-launch, complete shuttle weight of 531,000 kilograms (1.17 million pounds) to a cruise configuration of 3,893 kilograms (8,463 pounds).
The MSL cruise stage doesn’t work all that differently from the cruise control in a terrestrial car. Speeding along at a velocity (relative to the Sun) of 30,150 kilometres (18,734 miles) per hour, it will make a total of six corrections to its trajectory along the way. The flight computer is currently doing this using an on-board star scanner that tracks the position of the cruise stage in relation to the stars, powering up its hydrazine-fed propulsion system when required. Computers will monitor the spacecraft over the nine-month transit, pumping coolant around systems that get hot, like the solar panels, while insulating instruments sensitive to the cold from the near-absolute-zero temperatures of space.
On 5 August 2012, the MSL will enter the Martian atmosphere, 125 kilometres (78 miles) above the planet. It’s here that the aeroshell (a kind of heatshield) will separate itself from the now redundant cruise stage and begin its journey down to the surface. A parachute will deploy at 11 kilometres (6.8 miles) from the surface, and the aeroshell will fall away at eight kilometres (4.9 miles) as the MSL pings the surface of Mars with radar to adjust its position for an optimum landing. The entire backshell, parachute and all will separate from the MSL at an altitude of 1.6 kilometres (0.9 miles) where a new, rocket-guided landing system slows its descent. The final delivery system is a sky crane, which will lower Curiosity onto the surface for a soft landing.
Danger: Mars approaching!
The approach phase is one of the most dangerous parts of the MSL mission. Miscalculations could see the MSL spacecraft completely miss Mars or enter its atmosphere at a wrong angle, which would be catastrophic either way. So, 45 days before entering Martian atmosphere, NASA engineers will begin approach preparations by monitoring and updating the spacecraft’s altitude, as well as the correction manoeuvres that will adjust its trajectory upon entry. This will be done using extra requested time from the Deep Space Network (DSN) of terrestrial antennas located in Spain, Australia and the USA.
The landing site
Choosing the right landing site was critical. The last thing NASA wanted was to put Curiosity in a position where communication might be made difficult or in a region of less scientific interest. Although the rover is capable of articulate movement, at a speed of 144 metres (450 feet| an hour on smooth terrain, the area of Mars it can effectively explore during its mission is limited. Selection began in 2008 with NASA profiling an ideal landing site, which should have: ‘clear evidence of a past or present habitable environment’, a ‘favourable geologic record’ – meaning preserved layers of rock exposed at the surface, evidence of past water, good accessibility for the rover and all of this located near a safe landingzone. Sites were narrowed from over 30 candidates down to the final selection in 2011: Gale Crater, a 154-kilometre -diameter remnant of an ancient impact that has a mountain called Aeolis Möns that is five kilometres (three miles) high in its northern portion. In its 3.5 billion years it has formed sedimentary layers and has evidence of a wet history. Curiosity will land on a relatively smooth plain just north of Aeolis Möns.
Once Curiosity has been dropped off, then what? 40 years ago it was enough to get a man to the Moon and have him stick a flag in the ground. Today, despite the radical new methods involved in getting Curiosity to Mars, NASA’s requirements of any extraterrestrial mission extend far beyond bragging rights.
The nature of many of NASA’s future projects hinges on the success of the MSL’s innovative technologies. The target landing site, for example, is an area of around 20 kilometres (12 miles) in length, a fivefold improvement in precision using the sky crane/ rocket descent technique. Without this new tech, landing so close to the edge of the Gale Crater wall would be impossible. In a worst-case scenario, should the MSL lander fail to insert Curiosity safely or effectively into the landing zone, it may preclude similar Martian sites in the future. As the new system is capable of landing a vehicle even bigger than Curiosity (which is five times heavier than its predecessors, Spirit and Opportunity), a proven safe delivery onto Mars becomes even more important.
You’d have thought that, as Curiosity has been in development for nearly eight years, the NASA team would be keen to send the rover off to explore as soon as its wheels touch the ground. But as much as the scientists might like to do that, the engineers need to run a host of system checks that mean Curiosity won’t be going anywhere until at least five days after landing. During this time, they will essentially be ensuring that the wheels aren’t stuck and that the rover is capable of moving away from its landing position without embedding itself in soft sand, an irrevocable situation in which its predecessor Spirit found itself two years ago. But once that’s done, the fun part of the MSL mission starts…
The nature of this mission is one of discovery, so NASA hasn’t carved in stone exactly what the Curiosity will be doing in its 680 or so Earth days on Mars, though scientists do have a rough plan. Apart from maintenance and a 20-80 period (a Martian day, referred to as a sol, is nearly 40 minutes longer than an Earth day) when Mars is on the far side of the Sun, the Curiosity’s activities will be prioritised according to what it can find. The Curiosity has a much bigger range of movement than Spirit or Opportunity, rated for roaming up to 20 kilometres (12.4 miles) from the landing site. As a result, a major portion of its time will be taken up driving to scientifically interesting sites and collecting samples.
There is a huge range of possible ways the MSL mission might unfold in the Martian year that it spends there. However, using what we already know about Mars and the landing zone, NASA has compiled a number of day-to-day activities into logical sequences that form five separate scenarios, measured in tactical windows known as sols. Traverse sols mostly involve roving between target sites, triggered by a ChemCam observation. Reconnaissance sols involve surveying a site prior to detailed study, triggered again by the ChemCam plus the Mars Hand Lens Imager (M AHLI). Approach sols are triggered by a previous sol and place a patch of soil or rock within the working area of the rover’s robotic arm, while contact sols incorporate the arm-mounted instruments on the MSL to measure and observe a target.
Last but not least, sampling and analysis sols will most likely prove the most fascinating out of these five scenarios. The MSL will spend some time passing rock and soil samples through a sieve and into CheMin and Sample Analysis at Mars (SAM). In SAM, a suite of instruments will check for the presence of hydrogen, oxygen, nitrogen and other elements associated with life. Meanwhile, CheMin will check for minerals like gypsum and jarosite, which indicate the presence of water and might point to a previous Martian environment that supported life.
Curiosity’s first drive
After landing, but just before it takes its first ‘steps’, engineers need to run some important tests on the rover. Of primary concern is its initial footing and the terrain, which must be assessed so that the Curiosity can be moved safely away from the landing site. Then the MSL will go through a start-up sequence that includes measuring the air temperature, testing communications, unfolding the mast that carries the navigation camera, shooting images of its immediate surroundings and helping mission control pinpoint its precise location. Only then will Curiosity make its first foray across Mars.
Surviving winter on Mars
Martian winters are more brutal than even the coldest place on Earth. It can plummet as low as -143 degrees Celsius (-225 degrees Fahrenheit) in the negligible atmosphere of the polar ice caps. It gets so cold that the carbon gas in the atmosphere freezes at certain times in the Martian calendar, causing the atmospheric pressure to plunge. The main problem with Spirit and Opportunity wasn’t the cold, though – it was that they were solar-powered, which meant that during the dark periods they went into a state of hibernation with little or no activity. However, Curiosity has an independent power source, so it won’t have to work around the same constraints.
Life – but not as we know it…
Curiosity is a very versatile machine. It can measure the atmospheric pressure, humidity, wind speed and UV levels on Mars, detect radiation levels dangerous to humans, scan for minerals and gases trapped beneath the surface and take many gigabytes’ worth of images and video.
The rover is very tactile too, capable of examining scientifically interesting sites from a distance and then moving to them, scooping up soil samples, collecting and sifting through Martian rock, drilling to remove samples C with a mechanical arm, blasting the surface of boulders ,with a powerful laser and examining the plasma that ZK they emit. It can then analyse everything it has zapped, drilled, scooped and sucked up in a portable laboratory housed in its body that could rival a university chemistry lab. We know it can collect masses of useful scientific data, but what I can we expect to find, and what can we conclude ‘1 from that information?
NASA’s major goal in all the experiments that the MSL will conduct in its Martian year is to assess whether the processes on Mars indicate a planet that was ever capable of supporting life. A lifeless planet (or moon, such as Earth’s) that proves completely inert for billions of years could never have harboured life, for example. We know Mars has been subject to geological and atmospheric changes for millions of years, so the MSL is there to see what other changes the planet has experienced and to examine the finer details. Among other things, it will analyse sedimentary rock to see whether water was once present and look for evidence of ancient microbes, the simplest of life forms, in the rocks that will leave behind geological signatures, like ancient organisms that formed calcium carbonate (chalk) on Earth.
From a broader perspective, we’re very subjective judges of the conditions that lead to life – we only know for sure that the conditions on Earth led to life here. So one of the goals of the MSL is to build up a new picture of how other organisms might evolve, to help in the search for potential life around the cosmos. From MSL and Mars, NASA has other targets in the long term. Within our own Solar System, these include Titan, Europa and Enceladus, the frigid moons that orbit Saturn and Jupiter. Then maybe in the very distant future, we’ll be able to send a space laboratory beyond our own planetary system to those exoplanets with life potential, perhaps discovering the conditions for life somewhere else in the universe, whatever form it may take.
Keeping any scene of investigation clear of external influence is vital to a scientist. NASA is searching for the potential for Martian life, so minimising any terrestrial contamination is a major priority for the MSL. Contaminants are measured as ‘spores’ and might include Earth bacteria, dust and other synthetic materials. Throughout the project, NASA has gone to great lengths to keep the MSL as clean as possible, resulting in a spore count less than half the maximum set by NASA Planetary Protection Office regulations.
Keeping in touch
To receive commands and send data back to NASA, Curiosity will make use of terrestrial and Martian infrastructures. On Earth, three enormous antenna arrays consisting of dishes up to 70 metres (230 feet) in diameter make up the DSN (Deep Space Network). These are based in the USA, Spain and Australia. Communicating directly with the DSN can be costly in terms of Curiosity’s energy consumption and, due to the orbital position of Mars relative to the Earth and the Sun, it might not always be possible. Therefore sometimes Curiosity will uplink to two satellites orbiting Mars: the Mars Odyssey and the Mars Reconnaissance Orbiter. These are between 257 and 400 kilometres (160 and 250 miles) above the surface of the Red Planet, so are not only costing Curiosity less energy to send messages to, but they have Earth in their field of view for a lot longer, granting a larger window of communication.
While not the most consistent of meteor showers, the Leonids can be one of the most dynamic spectacles in an astronomer’s calendar. They’re a product of the comet Tempel-Tuttle, which has a radius of around 1.8 kilometres (1.1 miles) and has a 33-year cycle. The comet itself is fairly unremarkable compared to the likes of Halley’s or Hale-Bopp, however it leaves behind a dense stream of debris that results in a meteor shower rate that can reach as many as 300 meteors an hour.
Top 3 Mars rower lifetimes
1. Long – Sojourner – The Mars Pathfinder rover landed on 4 July 1997 and communications were lost just a couple of months later on 27 September 1997.
2. Longer – Spirit – The first of the two Mars Exploration Rovers landed on the Red Planet on 4 January 2004 and its final communication was received on 22 March 2010.
3. Longest – Opportunity – Spirit’s twin has been on Mars since 25 January 2004 and, amazingly, is still going, eight years on, having survived through five Martian winters.