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A huge volcano has been 'hiding in plain sight' on Mars.

Scientists have discovered the volcano near the planet's equator in the eastern part of Mars' Tharsis volcanic province.

It's still waiting for its official name, but for the moment it's being called Noctis volcano, and measures 280 miles in width.

That's about the same distance as between London and Cornwall and it's a bit taller than the tallest mountain in the world, Mount Everest.

The volcano can be found in a region called Tharsis which is home to three other giant volcanoes: Ascraeus Mons, Pavonis Mons, and Arsia Mons.

While the diameter of Noctis is larger than the others, it looks more eroded and therefore isn't as tall.

It's this erosion that means although it's been photographed many times since 1971, no one has spotted it until now.

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Scientists reckon the volcano has been active for a long time and there might still be glacier ice underneath the huge structure.

They say it's a significant discovery because it provides a new location to study Mars' in greater detail including looking for life there.

Dr Pascal Lee is a planetary scientist with the SETI Institute and the Mars Institute based at NASA Ames Research Center, and the lead author of the study.