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.
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.
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?
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
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.
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.
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
Martian experiments
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.
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…
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.
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
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?
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.
Clean machine
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.
The Leonids
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.