A vehicle journey of just over 22 miles hasn't really been cause for celebration since the dawn of the motor car itself, when low speeds and unpaved roads made it more arduous than it would have been on the equine alternative.

But transpose that figure to another planet and well, it starts to look a bit more impressive.

That 22 miles is how far one rather famous electric vehicle has traveled on the surface of the "red planet", Mars.

According to NASA, via Space.com, Opportunity rover has covered that distance since 2004, examining the planet's surface and relaying data back to its controllers at NASA.

Another planetary explorer, Curiosity rover, is also making tracks (literally) across Mars, having covered 0.4 miles since landing last year.

Driving distances on other planets (Image: NASA)

Driving distances on other planets (Image: NASA)

While those distances might be well within the reach of modern electric cars here on earth, the time they spend operating is significantly longer. As such, regular lithium-ion batteries alone don't suffice.

The large Opportunity rover uses solar panels to gather sunlight through the thin Martian atmosphere, and batteries to store power for times when the sun isn't shining.Curiosity goes a step further by using nuclear power--its radioisotope thermoelectric generator (RTG) generates electricity using the radioactive decay of plutonium-238.

You'd not want it in your car, but RTGs have quite a track record--both Voyager spacecraft launched in the 1970s used RTGs, and both are still sending signals back from the edge of interstellar space. Voyager 1, launched in 1977, is 124 Astronomical Units from earth--124 times the distance from earth to the sun.

Both Martian rovers have plenty of life left in them then, and while their inch-by-inch pace might seem agonizingly slow, they're every bit as impressive as the best modern electric cars.

In fact, next time someone tells you electric cars are useless, just ask them how far they think a gasoline-powered vehicle would get on the surface of Mars...

[Hat tip: Brian Henderson]


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