Robot explorer finds ancient lakes on Mars

The Mars rover Curiosity has found evidence that water once flowed on Earth’s next-door neighbour. Why is this exciting? Because where there is water, there may be life.

Curiosity, the squat robot roving the surface of Mars, has made a momentous discovery: a tablespoon-sized sample of grit and sand which could provide evidence of alien life.

The discovery might not seem very inspiring – it contains little that could not be found in an average garden. But amid the dirt, Curiosity detected a cocktail of minerals and elements that could once have supported simple organisms.

For NASA scientists, analysing data transmitted over 200,000 miles through space, it is mission accomplished. Curiosity was sent to Mars to determine whether the planet had ever harboured a ‘habitable environment’; today, they can say unequivocally that ‘the answer is yes.’

Vital materials in Curiosity’s sample included the key chemical ingredients for life, carbon, sulphur and oxygen among them. But more crucial still was a smattering of clay minerals that could only have formed in the presence of fresh, neutral water.

This is exciting because, as far as we are aware, every life form in the universe depends on water. If pure water was present on Mars, microbes may have existed there too. And if our neighbouring planet has the conditions for life, habitable environments could be more common than previously thought.

Why is water so important? Because it is a solvent which has liquid form at unusually high temperatures. This surprisingly rare combination makes water an environment in which chemicals can interact. A primeval sea facilitated the generation of amino acids that first spawned life on Earth, and ever since then, Earth’s organisms have used water to transport chemicals and allow them to react.

As a vapour, water is helpful too: it captures heat and keeps a planet’s surface steady, then descends from clouds as rain or snow, maintaining a dynamic environment for life.

So water is a rare and wonderful thing. But some scientists suggest that it may not be so unique. Ammonia or hydrogen fluids could also support life forms, they believe, perhaps even in our own galaxy – though these creatures would be very different from anything we know.

Second life?

So why are we so fixated on finding water? Because, some chemists say, we are too egocentric and mentally limited to imagine life forms that are not like us. Alien life might be weird beyond our wildest dreams; we should broaden our search and open our minds to whatever the universe has to offer.

But others defend our aquatic obsessions: organisms founded on something other than water would be so unfamiliar that we would not recognise them as life at all. Such a so-called ‘life form’ would go down as just some strange and impenetrable phenomenon; the question we are really fascinated by is whether or not we are alone.

You Decide

  1. Which would be a more exciting discovery: organisms that were similar to those on Earth, or organisms that were so wildly different that we would struggle to recognise them as ‘life’?
  2. Science fiction writer Arthur C Clarke once said: ‘Two possibilities exist: either we are alone in the universe or we are not. Both are equally terrifying.’ Do you agree?

Activities

  1. Make a poster showing water’s chemical structure and listing as many of the compound’s distinctive qualities as you can think of.
  2. All organisms on Earth are known as ‘carbon-based’ life forms. Write a brief explanation of what this means.

Some People Say...

“Everything in the universe that’s interesting happens right here on Earth.”

What do you think?

Q & A

Does this mean I’ll get to meet a Martian someday?
It’s unlikely. Curiosity hasn’t actually discovered a life form, just conditions that could possibly have supported one in the past. And even if Mars did harbour life, it would almost certainly be microscopic, single-cell organisms of an extremely primitive kind: for walking, talking extraterrestrials we will have to look a little further afield.
And are we?
The Search for Extraterrestrial Intelligence (or SETI) has been looking for signs of sentient life for decades. Powerful radio telescopes scan the skies, pulsars send out signals to alert aliens to our presence and physicists scan distant stars for unusual electromagnetic patterns. Scientists are deeply divided over the chances that these efforts will be fruitful.

Word Watch

Curiosity
This ‘Mars rover’ is a laboratory on wheels. It is equipped with a drill and 17 cameras, and packed with sophisticated systems for analysing the materials it collects.
Over 200,000 miles
Because Earth and Mars take different periods to orbit the sun, their distance from each other fluctuates hugely. At present it is almost as far from us as it ever gets: it will soon be almost directly behind the sun. This will prevent NASA from communicating with Curiosity for a month.
Habitable
This word, from the same Latin root as ‘have’, ‘habit’ and ‘habitat’, simply means that an environment can support life.
Primeval
Belonging to the earliest era: exceptionally old or ancient.
Our own galaxy
Some suspect that Titan, a moon of Saturn, could harbour a life form based on hydrogen fluids.
Very different
Nobody knows exactly how life would look without water, but it would probably be based on the element silicon instead of carbon. One outlandish theory says that silicon-based life forms may survive by feeding on minerals and rocks!

Subjects

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