InSight lifted off in May and is expected to land on Monday, but it's just one of dozens of robotic and satellite missions that humanity has rocketed to Mars over the decades.
These spacecraft have beamed back dazzling photos, inspired sci-fi movies like "The Martian", and even helped give Elon Musk, the founder of SpaceX, the idea to colonise the red planet with the Big Falcon Rocket.
While scientists readily admit they have much to learn about Mars, including the planet's internal structure (a mystery InSight will try to solve), what we have found out so far is incredible.
Here are 13 fascinating facts about Mars and our robotic exploration of the red planet.
Olympus Mons is more than twice as high as Hawaii's Mauna Loa, the tallest mountain on Earth from top to bottom.
Compared to the Grand Canyon on Earth, Valles Marineris on Mars is nearly five times deeper, about four times longer, and 20 times wider.
The red planet doesn't have plate tectonics, which is what causes most quakes on Earth. But rising plumes of magma could trigger Mars quakes, as could meteorite impacts and the contraction of the world due to cooling. InSight will listen for them with its seismometer.
If aliens existed on Mars, they might have lived in oasis-like pools. These pools would have been habitable for life, just as they are on Earth.
Martian oceans also had tsunamis like those on Earth. The tallest may have reached as high as 123m.
Like Earth, Mars has ice caps at its poles. The northern cap is up to 3.2km deep, is a mix of water and carbon dioxide, and covers an area about half the size of South Africa.
The average surface temperature on Mars is -63 degrees Celcius, 138 degrees chillier than on Earth. But on a mid-summer day at the red planet's equator, temperatures can peak at a balmy 35 degrees Celcius).
Mars has almost as much surface as Earth has land - but that doesn't account for the 71% of Earth that's covered in water.
The Martian atmosphere is 61 times thinner than Earth's, and it consists almost entirely of carbon dioxide, which makes up just 0.04% of Earth's atmosphere.
On Earth, sunsets are a brilliant mix of reds, pinks, oranges, yellows, and other colours. But on Mars they're blue. Because air is dozens of times less dense on the surface of Mars than it is on our planet, white sunlight refracts less - leading to fewer colours (primarily blues).
Missions to Mars have become much rarer - after 23 launches in the 1960s and 1970s, we've launched just 10 in the new millennium (so far). This count doesn't include InSight.
Getting to Mars is hard: About a third of the missions launched have failed.
NASA is hoping to add InSight to the "success" column on November 26.
This story has been updated. It was originally published on June 1, 2017.
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