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Curiosity – its amazing journey, and some fun facts

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At 899 kg (1,982 lbs) Curiosity is more than 5 times the weight of its predecessors Spirit and Opportunity, making it the heaviest rover sent to Mars so far. Curiosity is 2.2 m tall (7.2 ft) which is a bit taller than the average height for a basketball player. Image 1 below offers a size comparison with previous Mars rovers: Curiosity’s test rover (on the right), Sojourner’s test rover (in the foreground) the Opportunity test rover (on the left), and some regular-size scientists (center).

A size comparison of Curiosity beside other Mars rovers

Image 1: Curiosity size-comparison (Image credit: NASA/JPL-Caltech).

The Curiosity rover was a component of the Mars Science Laboratory (MSL), which started its journey in the Atlas V rocket on November 26, 2011. It was placed in the payload fairing (see image 2) which is the nose cone that protected the MSL during the ascent through the Earth’s atmosphere. The payload fairing used to transport the MSL was 5m (16 ft) in diameter and 20.7 m (67.9 ft) long.

The payload fairing used for the Curiosity Mars rover

Image 2: The payload fairing for Curiosity (Image credit: NASA).

The Atlas V rocket (58.3 m or 191 ft tall) is an active expendable launch system, i.e. non-reusable. Since the first launch of this type of rocket in August 2002 it has had more than 70 successful mission, though two of them (in 2007 and in 2016) had slight anomalies during their flight. Inside the payload fairing the MSL was placed on top a rocket called the Centaur upper stage. This rocket was used to get the MSL into low orbit and then to accelerate it out of orbit and its correct trajectory towards Mars.

Forty-two minutes after liftoff the MSL spacecraft separated from the Centaur upper stage and it was finally on its way to Mars, traveling 352 million miles over 8 months. The landing process was famously called the ‘7 minutes of terror’ as this was the first time such a landing technique had been attempted. Curiosity approached Mars at an estimated 20,900 km/h (13,000 mph) and before entering its atmosphere it conducted a series of maneuvers to tilt the craft so the heat shield would be facing the atmosphere. The entry into the atmosphere decelerated the craft, and once it reached a velocity of 1,450 km/h (900 mph) the parachute deployed. This slowed down the craft quite considerably, to a mere 595 km/h (370 mph). At this point the craft was still 9 km (5.5 mi) above ground. At one mile above ground the craft separated from the parachute, and 8 retrorockets powered up to slow the craft even further. At around 20 m (65 ft) from the ground the ‘sky crane’ lowered Curiosity using tethers. It then waited for the signal of slack in the cables, and confirmation of safe landing from Curiosity, to cut the cables and fly off to crash far away from Curiosity’s landing site.

7 minutes of terror as Curiosity landed on Mars

Image 3: The '7 minutes of terror' (Image credit: NASA/JPLmage).

Since arriving on Mars Curiosity has been hard at work, making discoveries upon discoveries. It has found evidence of water on the ground, and oxygen in the atmosphere in Mars’s distant past. It has also detected life’s building blocks in rocks, and higher than expected radiation at ground level during solar storms. It’s given us a new closer look at Mars, and what conditions humans will face when they finally arrive on the red planet. In 2017 Curiosity celebrated 5 years on Mars, and by then had traveled 10 miles across Gale Crater and up Mount Sharp. In that time it has also taken well over 400,000 images. Curiosity has survived well past its one Martian year primary mission time, despite the harsh conditions on Mars’s surface. We are now looking forward to all the new discoveries and images (especially the selfies) it will probably send us in the 8 years or more of what’s left of its lifespan.

Some fun facts about Curiosity

Each of Curiosity’s six wheels has its own motor, and some have their own steering. This allows Curiosity to climb over obstacles as high as 76 cm (30 inches). The wheels have Morse code patterns cut into them which spells out JPL as the rover rolls around Mars. This is used by scientists on Earth to estimate the distance traveled by the rover.

The wheels of the Curiosity Mars rover, with JPL in Morse code

Image 4: Curiosity's wheels (Image Credit: NASA, JPL-Caltech, MSSS, MAHLI).

MSL’s parachute is 15 meters (51 feet) in diameter and has 80 suspension lines. It’s referred to as ‘supersonic’ because it can withstand deployment at Mach 2.2 (2,714 km/h or 1,687 mph). See below (image 6) for comparison to other regular-size scientists.

The parachute of the Curiosity Mars rover

Image 5: Curiosity's parachute.

Curiosity has a total of 17 cameras on board, and 10 scientific labs. Its on-board computers have only 2 GB of storage space: a typical iPhone 4S has 4 times more computing power than that! However Curiosity has a nuclear battery that should keep it going for 14 years … which is considerably longer than a regular phone battery, and also longer than its one Martian year mission (equivalent to 687 Earth days) should require. As part of its regular self-checks, Curiosity takes 70 or more images of itself, which are used by NASA to create composite ‘selfies’. These images are not only useful to the teams on Earth to visually check how well Curiosity is doing, but are also a great way to gain and keep public interest. Image 7 (below) is a beautiful selfie taken May 11, 2016, with Mount Sharp on the horizon.

A selfie of the Curiosity Mars rover

Image 6: A Curiosity 'selfie' (Image credit: NASA/JPL-Caltech/MSSS).

And finally, did you know that Curiosity sings Happy Birthday to itself every year on August 6? I guess it’s a bit lonely out there. But maybe humans will join Curiosity on Mars one day.

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