Blueberries on Mars

The story

Far, far away, there is a whole planet the colour of rust. It is called Mars. No people live there, and nothing alive has ever been found — just red rocks, red sand, dust and wind, with ice hiding in the coldest places.

So how could we ever look around a place like that?

We sent a robot. A brave little robot called Opportunity, about the size of a golf cart, with camera eyes on a stalk and six wheels for feet.

Getting down was the wild part. Opportunity fell toward Mars wrapped up in a big bundle of airbags — and it BOUNCED. Boing! Boing! Boing! — bouncing across the red ground like a giant beach ball, until it rolled to a stop. When the airbags let go and the lander opened like a flower, the robot found itself somewhere lucky: a small hollow, facing a wall of rock with stripes in it. Layer on layer on layer, like pages.

That matters, and I'll tell you why. To the scientists back home, rock layers are like a book: each layer laid down long ago, one on top of another. Read the layers, and you can read what happened here — even before there were any people anywhere.

So Opportunity got to work, pressing its tools right up against the rock the way you might press your nose to a window. And scattered in the rock, and lying all over the ground, it found something wonderfully strange.

Tiny round stones. Little grey balls, small as peppercorns, everywhere. Not real blueberries, of course — little round STONES, the size and shape of blueberries — but the scientists loved the nickname, and it stuck.

And those blueberry stones were a clue. The biggest clue of all. Because round stones like that, on our planet, grow inside rock when WATER seeps slowly through it. Water, sitting in the ground, minerals gathering into little balls, ever so slowly. And the salts in the rock told the same tale.

Do you see what the little robot had found? Mars was not always a dry red desert. Long, long ago, there was water here. Water soaking the ground. Maybe pools of it, shining under the sky, coming and going, on the very spot where Opportunity stood.

The little robot was only supposed to work for three months. It worked for nearly fifteen years. It drove and looked and pressed its nose to rock after rock, sending its postcards home, until one day a great dust storm spread around almost the whole planet and hid the Sun. Opportunity ran on sunshine. The sky went dark. The little robot went to sleep, and did not wake up.

But nothing it found is lost. The little blueberry stones are still there, scattered across the red sand, and newer robots are rolling on, reading further pages of the rock.

So now you know a secret about the red dot in the sky: Mars keeps its story written in stone — and one of its greatest readers was a brave little robot that bounced.