Mission Mars

Exploration The moon and Mars have always fought for the attention of earthlings. Mars has won this round. Sivaram C discusses rover Curiosity’s imminent landing on the red planet and what it entails.

While the Olympic Games are being held on Earth in the first two weeks of August, Mars will be visited by a well-equipped messenger from Earth i.e. the Curiosity Rover spacecraft! Its nearly eight-month journey began in December 2011.

Weighing nearly a ton, it will be the heaviest of the four rovers which have already been exploring Mars for the past fifteen years. It weighs twice more than the combined weight of the Spirit and Opportunity Rovers!

These rovers have traversed over a lot of Martian soil in the past eight years. Curiosity, however, is not headed for Olympus Mons (at 26 km, the tallest mountain on Mars), but will land (sometime after August 6) in the somewhat small Gale Crater, chosen after a careful survey of sites photographed in detail by the Mars Reconnaissance Orbiter (MRO), which has been orbiting Mars for a decade.

Mars exploration began almost 50 years ago, with the flyby of Mariner 4, in July 1964.

After several trips by both American and Russian spacecraft, the Viking Landers finally landed a whole laboratory in July 1976, in order to conduct detailed study, including a search for microbial life.

 It was not found! However, in the past fifteen years, the combined work of four orbiters – two rovers and a polar lander – has provided a new picture of Martian geological history and the role played by water.

It transpires that Mars had an early wet era, when thin films of water reacted with air molecules (in the then much thicker atmosphere) to form sulphates, oxides and clay-rich rocks. The Gale Crater’s eight kilometre high central mountain, as revealed by MRO, has layers of sulphates and clay which require water to form. As Curiosity approaches the mound’s base it will encounter Mars’ most ancient rock containing clay.

Explore minerals

It will also explore sulphate minerals i.e. it will explore the watery history of Mars in chronological order. It carries an impressive array of instruments. It is not powered by solar energy panels like the earlier rovers (Spirit and Opportunity), but by heat of the decay of five kilograms of plutonium-dioxide.

This is expected to power it for at least one Martian year (687 days) in the initial phase and allow it to traverse about 20 km during this period with the target of analysing between twenty to fifty samples (although distance wise, the Opportunity rover has already travelled about 40 km). There is enough fuel to last a decade in the RTG.

Its vast array of sophisticated instruments include the navigation camera (navcam), chemistry camera (chemcam) and mastcam (to image in colour surrounding rocks).
The chemcam will remotely analyse rock. Inside the rover, there are SAM (sample analysis at Mars), chemin (chemistry and Mineralogy), neutron detector and alpha particle spectrometers, while on the robotic arm there are drills and powder drills (to pulverise rocks with laser before analysis) as well as many sieves, scoops and brushes!

It will figure out whether the clay and sulphate rich rocks hosted Martian life when they formed. The Curiosity is not really designed to detect arean life, living or dead! So even a negative result cannot establish for certain whether Mars ever harboured life! But, it must be remembered that even finding fossils within three billion year old Earth rock is a onerous task – like looking for a needle in a haystack.

Sign of life

Due to prior thorough orbital mapping, especially by MRO, Curiosity is almost sure to find rock that formed in the presence of water although finding organic materials (a sign of life) is much harder. The Martian polar lander Phoenix, in 2008, made the startling discovery of oxidisers like perchlorate and found water ice just below its resting place on Martian soil.

The Curiosity is too heavy to land on Mars with the technique adopted for the landing of the earlier rovers beginning from Sojourner. A new technique, the sky crane is to be used – the mother ship will use retro-rockets to hover twenty metres above the surface and gently lower the rover to the ground on cables.

The rover’s large parachute, 16m across, makes sure it touches down at less than a metre per second and was tested 2 years ago in the world’s largest wind tunnel!
While the instrument SAM will focus on molecular chemistry in the atmosphere especially methane, chemin will identify elemental abundances of sampled soil and rock.

It can measure composition directly. Scientists do not expect Curiosity to find evidence of life on Mars, but if SAM finds methane, they would like to compare its concentration with that of Earth, where most of it is of biological origin. Both the above instruments have reusable sample chambers enough for more than seventy analyses.

If any interesting rock or sample is suspected, the rover will be ordered to approach and place it on its robotic arm for analysis! The rock would be pulverised and pushed through a tube into a set of sieves called CHIMRA.
The name ‘Curiosity’ given to the latest Mars rover was the winning entry (by 12-year old Clara Ma) in the naming contest that inspired nearly ten thousand entries from students aged 5 to 18!

While we, on earth, are looking forward to the London Olympics, Martians and planetary space scientists on Earth will be having an equally exciting time following Curiosity’s August visit to Mars.

As a high percentage of Martian space missions have flopped (including the latest Phobos-Grunt mission, six months ago), one would wish it the best possible luck!