Mars Curiosity Rover: how big, how fast, how much and what can it do?

On Monday August 6 at 3.17pm AEST NASA’s Mars Curiosity Rover landed safely on the surface of the red planet. For the next two Earth years or so it will roam the surface of Mars looking for signs of organic life on our near neighbour.

And today, the big rover that could took its first tentative drive around the red planet. But what of this piece of scientific and automotive engineering? How does it stack up against the vehicles we drive every day on our home planet?

How big is it?

Images on TV make the Curiosity seem like a tiny little thing. It’s not. In fact, it’s taller and wider than any car you buy today.

All up the Curiosity Rover measures 3 metres lengthwise (that’s about the same as original Mini and half a metre shorter than the current Fiat 500), 2.7 metres wide (let’s call it 0.7m wider than the Ford F-150 pick-up) and 2.2 metres tall (oooh, that’s about 20cm taller than the Hummer H1).

What powers it?

The Curiosity is the biggest autonomous rover we’ve sent anywhere in the solar system and it easily dwarfs NASA’s previous efforts, the Spirit and the Opportunity. Roughly, the measured up at 1.6m long, 1.5m tall and 2.3m wide. Both tipped the scales at a relatively lightweight 180kg; the Curiosity tips Earth-bound scales at 900kg.

This means that unlike the Spirit and Opportunity, which are powered by solar panels, the Curiosity requires a power source with a bit more oomph. So, it relies on a form of nuclear power called radioisotope thermoelectric generation. Within a graphite cannister there’s about 4.8kg of plutonium-238 that’s slowly decaying radioactively, giving off heat and generating about 125W of electricity.

There are two lithium-ion battery packs on-board, allowing Curiosity to store excess electricity when it’s resting or doing less power intensive activities. This also enables the rover to use several of its instruments in concert.

How does it traverse Mars?

The Curiosity rides on six aluminium wheels with tread patterns and cleats cut into them; there are no tyres. Each of the 20-inch wheel sits at the end of an articulating leg that allows the rover to traverse of over rocks up to the diameter of its wheels.

There’s an electric motor powering every wheel, and the two wheels at the front and two at the back steer as well. This means that the Curiosity has turn up to 360 degrees in the same spot. In fact, it can do a bit of rudimentary digging by locking five of its wheels in place and rotating the sixth.

How quickly will she do 0-100km/h?

To hit 100km/h, Curiosity would probably need to push itself off a mountain so steep that rover’s anti-rollover systems would go into meltdown. NASA quotes a top speed of 40mm per second, which translates to about 0.144km/h. In reality, Curiosity will probably average half that when it’s on the move.

It doesn’t need to carry anyone, so what’s inside the body?

That be where all of Curiosity’s sensitive electronics are hiding. Unlike Earth, Mars is a pretty rough and tumble place to be, even for a travel-crazy extraterrestrial rover. Not only does the metal box keep the rover’s brains protected from the fine Martian dust, there’s a liquid filled series of pipes that ensure that the electronics are kept at an optimum operating temperature — the temperature on the surface of Mars, where the rover landed, can vary between -127 degrees Celcius and +30.

There are two computers — one acts as a backup — powered by a RAD750 CPU with 256MB of RAM at its disposal and 2GB of flash memory to work with. The bulk of the computers’ work is done in concert with the Inertial Measurement Unit that allows the rover to sense its movement in three axes — vertical, horizontal and yaw (side-to-side) — and plot out its movements.

Because of the distance between Earth and Mars, as well as the limited communication windows available, mission control basically sets the rover’s destination and navigating there is up to Curiosity itself.

It can drive around, but what else can it do?

Scattered around Curiosity is an array of 17 cameras, seven of these are carried on a mast protruding from the rover’s body. Some cameras act as the rover’s eyes, viewing the world around it in 3D black-and-white and sizing up all the objects around it. Others view in colour and 3D, and feature zoom lenses enabling Curiosity to take all those happy snaps we’ve seen.

Atop the mast is a laser that can zap objects from a distance to see what’s in its vapour and quickly determine whether it’s worth driving over there. Curiosity also features an arm and a hand that can grind away at rocks, as well as performing sophisticated elemental analysis.

How do we communicate with Curiosity?

The rover can talk to mission control either directly or via the two spacecraft currently orbiting Mars. As Curiosity doesn’t need to transmit as far, transmission rates to and via those spacecraft are quicker. Things slow down to around 32kbit/s when Curiosity and Earth talk directly.

Depending on where the planets are in their orbit around the Sun, the distance between Earth and Mars varies between 54.6 and 401 million kilometres. This means that a signal takes between 3 and 22 minutes to travel between us.

And the cost?

A cool US$2.5 billion dollars. That includes the Curiosity Rover, launch equipment, spacecraft to get to into Mars orbit, and the descent and landing module, including the innovative Sky Crane.

Derek Fung

Derek Fung

Derek has a lifelong love for all things automotive, from the dullest Camry to record shattering Bugattis. Prior to starting up Between the Axles he was a reviewer for CNET Australia and the founding editor of its Car Technology channel. [Read more]