Devangshu Datta: Roving eye on Mars

Until the mid-17th century, the speed of light, which is about 300,000 kms/second, was assumed to be infinite. Engineers reckon in practice that electronic communications will be near-instantaneous, when they design remote-controlled or telemetering devices.

Things change when astronomical distances are involved. The moon is roughly a couple of light seconds away, which is bad enough. Mars, at its closest to Earth, is over three light minutes away and it’s more than 22 minutes away at its most distant.

So, the Curiosity Rover (and every other mission to the fourth rock from the sun) is entirely on its own. Radio signals take so long that monitoring, or giving orders in real-time, are impossible. The “seven minutes of terror”, when the 900 kg rover entered Mars’ atmosphere and landed, was long over before ground control at the National Aeronautics and Space Administration (Nasa) received the news.

Distance seriously complicates Mars missions. Even getting there involves arcane calculations. Mars and Earth have concentric, elliptical (egg-shaped) orbits around the sun. The Mars orbit is more distant and more eccentric. The ideal launch windows pop up only every 26 months or so. It takes nearly nine months (253 days in Curiosity’s case) to get there. The only mission ever designed to return with samples, the Russian Phobos-Grunt, failed.

Curiosity carried out a near-flawless landing, which took about one second more than simulations. The navigation was good since it arrived about 2.4 kms from the originally designated point in the Gale Crater. It did sustain some damage to one wind sensor.

It had to have new software installed once it landed, to carry out its real task of exploration and scientific experimentation. The process of uploading new software took days but all seems well so far. The rover has just taken its first tentative steps on Mars itself, moving about 3 metres and then returning to its landing spot, while turning around and performing a few manoeuvres. It has also tested its laser by zapping rocks.

The space laboratory is designed by an international team. The multitude of experiments have four main scientific goals. Curiosity has to determine habitability, the availability of water, and also study the climate and geology of the planet.

Mars has a substantial atmosphere, 95 per cent carbon dioxide with traces of methane and oxygen. The geology shows signs of lava flows, which means volcanic action has occurred. Not much data exists on the radiation signature and magnetic characteristics.

The planet has a gravity of around 40 per cent that of Earth and it has polar ice-caps. Initial temperature readings show diurnal (the Mars day is 24 hrs, 37 minutes) variations of between minus 90C and plus 4C. There are cave systems where temperatures ranges could be less extreme.

It is quite conceivable that the planet has life, or it did have life in its past, given these conditions. The excitement in UFO-hunting circles over bright lights seen moving on the horizon of some images seem misplaced, however. Dust on the camera lens is the likely explanation.

If all goes well, Curiosity will spend the next two years learning as much as it can. The 900 kg, six-wheeler is nuclear-powered, which means it has no issues about running out of “juice”. It also has massively redundant communications. The data it collects will be digitised and sent back. Its robotic arm has a toolkit to collect and analyse samples.

While robotic arms, nuclear reactors and autonomous vehicle systems are all proven technologies, and capable of handling very challenging terrain, the light gravity could make a big difference to the functioning. Eventually, the rover is supposed to climb up the slopes of Mount Sharp, which rises 5,000 metres above Gale Crater.

As the “habitability” parameters of the science mission suggests, the data are vital for the future of Nasa’s plan to eventually launch a manned Mars mission. That will be a different ball game altogether in terms of difficulty.

At the minimum, a manned mission will demand that the crew spends about nine months travelling there. Then they spend another 26 months or so living on Mars and finally, another nine months travelling back.

Crews in nuclear submarines are known to spend six months at a stretch underwater and the International Space Station can manage on one supply mission a year. But the logistics of food, air and water supply are much more daunting for a four year mission. The psychological effects of isolation for that length of time will undoubtedly be severe and difficult to map as well.