Red Planet, Blue Past: The Hunt for Water on Mars
Scientists send rovers to Mars to search for clues that liquid water — and perhaps life — once existed there.
Imagine a world where rivers once flowed, lakes shimmered under an alien sun, and rain fell on red rocks. That world was Mars — and scientists believe it looked very different billions of years ago from the dry, dusty place we see today.
Mars is now a freezing desert, with a thin atmosphere and no liquid water on its surface. Yet rovers — robotic vehicles sent from Earth — have found some extraordinary evidence that this was not always the case. Rocky formations that look like ancient riverbeds, smooth pebbles that could only have been shaped by flowing water, and minerals that only form in wet conditions have all been spotted on the Martian surface.
But why does water matter so much? On Earth, wherever we find water — even in scalding hot springs deep underground or in the icy waters of the Antarctic — we find life. Tiny microbes thrive in the most hostile environments imaginable, as long as there is liquid water nearby. If Mars once had water, it may also have harboured simple life forms, even if only microscopic ones.
The rovers sent to Mars are equipped with an impressive array of scientific instruments. They drill into rocks, analyse soil samples, take thousands of photographs, and send the data back across millions of kilometres of space. The rover Curiosity, which landed in Gale Crater in 2012, found compelling evidence that the crater was once a lake that persisted for millions of years. Its successor, Perseverance, landed in Jezero Crater in 2021, a place scientists chose because it appears to be an ancient river delta — the fan-shaped area where a river once met a lake.
Perseverance has been collecting small tubes of rock and soil, carefully sealed to preserve any ancient material inside. A future mission is planned to bring these samples back to Earth, where laboratories far more powerful than anything a rover can carry will examine them for traces of past life.
The search is painstaking and slow. Mars is an enormous distance from Earth, and signals travelling at the speed of light still take several minutes to arrive. Scientists must plan every movement with great care, since a stuck wheel or a wrong turn could end a mission that cost hundreds of millions of pounds.
Yet the rewards could be astonishing. If signs of ancient life were found on Mars, it would be one of the greatest discoveries in the history of science. It would suggest that life is not unique to Earth — that in the vastness of the universe, we may not be alone after all.
Words to know
- harboured:
- Provided a home or shelter for something — here, Mars may once have 'harboured' living things, meaning it supported them.
- painstaking:
- Done with great care and close attention to every detail, even when it takes a very long time.
- microscopic:
- Far too small to be seen with the naked eye — you would need a microscope to spot it.
Word of the week: extraterrestrial
Relating to, or coming from, somewhere beyond planet Earth. Example: The discovery of ancient microbes on Mars would be the first confirmed example of extraterrestrial life. Similar words: alien, otherworldly.
Science corner: How Do Rovers Actually Move?
A Mars rover looks a little like a six-wheeled go-kart, but it is one of the most sophisticated machines ever built. Each wheel is independently motorised, meaning the rover can turn in almost any direction, and the whole body can tilt and flex so that it keeps moving even over very rocky ground.
Rovers travel very slowly — often just a few centimetres per second — because the landscape is uneven and a tumble could end the mission permanently. Scientists on Earth plan each drive carefully using maps built from photographs, choosing the safest possible route.
Power comes mainly from solar panels, which soak up sunlight to charge batteries that run the rover's systems through the Martian night. Perseverance, however, uses a small nuclear power source called an RTG, which works even during dust storms when sunlight cannot reach the solar panels. It is a clever solution for one of the most hostile places in the solar system.
On this day in history: The First Magnetic North Pole Expedition Returns (19 October 1899)
On 19 October 1899, the Norwegian explorer Fridtjof Nansen returned to a hero's welcome after completing remarkable scientific voyages in the Arctic. Nansen had pioneered the use of specially designed ships to survive being frozen into sea ice, drifting with the current to gather scientific data about the polar ocean. His careful observations of ocean currents, water temperature and ice behaviour transformed what scientists understood about the Arctic environment. His approach inspired generations of polar explorers who followed, and the scientific methods he developed for working in extreme cold are still reflected in polar research today.
Did you know?
- Mars has the largest volcano in the entire solar system — Olympus Mons — which is about three times the height of Mount Everest.
- A day on Mars lasts just over 24 hours and 37 minutes, making it the most similar to an Earth day of any other planet.
- The Mars rover Opportunity, designed to last 90 days, kept working for nearly 15 years before its mission finally ended.
- Smooth, rounded pebbles found by Curiosity are strong evidence of flowing water, because only moving water shapes stones in that way.
Joke corner
- Why did the Mars rover bring an umbrella? Because it heard there used to be showers on Mars!
- What do you call a sleeping dinosaur on Mars? A Martian-saur — it's been resting for millions of years!
Talk about it
If you could ask a Mars rover one question and it could somehow send back an answer, what would you ask it — and why?
What do you think?
What do you think it would mean for humanity if scientists discovered that life had once existed on Mars?
