Solar eclipses are awesome to view on Earth, but of course, we’re not the only planet to have them.
NASA’s Curiosity Rover, currently ensconced on the Red Planet, captured not one but two eclipses, as both Mars’ moons, Phobos and Deimos, passed in front of the Sun last month.
When Curiosity landed on Mars in 2012, it took with it what NASA’s Jet Propulsion Laboratory (JPL) call its “eclipse sunglasses”, filters that allow its Mast Camera to stare directly at the Sun.
On March 17, or Sol 2,350 of the mission (a Martian day, or Sol, is 24 hours and 37 mins), Curiosity’s MastCam witnessed Mars’ smallest moon, Deimos, pass in front of the Sun. Deimos is only a tiny moon, lumpy shaped, and looking more like an asteroid than a moon. In fact, it’s so small – a mere 2.3 kilometers (1.5 miles) across – that it’s technically more of a transit than a proper eclipse.
That doesn’t mean it’s not incredibly useful to document its transit and learn more about its strange orbit. After all, the first time a Mars rover tried to image Deimos transitting, scientists discovered the tiny satellite was 40 kilometers (25 miles) away from where they had thought.
Deimos transitting. The images here have been sped up by a factor of 10. NASA/JPL-Caltech/MSSS
On March 26 (Sol 2,359), Curiosity also snapped Phobos, Deimos’ big brother, eclipsing the Sun. Phobos is a lot more dramatic than Deimos in many ways. It’s bigger, at 11.5 kilometers (7 miles) across, and orbits Mars three times a day from just 6,000 kilometers (3,700 miles) away, closer than any other moon does its planet in the Solar System. In fact, Phobos is edging closer to Mars at a rate of 1.8 meters (6 feet) every 100 years. At this rate, it will either crash into Mars or break up into a ring in around 50 million years.
Phobos, Deimos' big brother. The images here have been sped up by a factor of 10. NASA/JPL-Caltech/MSSS
Curiosity and its predecessors, Spirit and Opportunity, have observed Phobos eclipsing the Sun 40 times, and Deimos transitting eight times, and each time we refine our knowledge of the Red Planet and its moons.
"More observations over time help pin down the details of each orbit," Mark Lemmon, a co-investigator with Curiosity's Mastcam, said in a statement. "Those orbits change all the time in response to the gravitational pull of Mars, Jupiter or even each Martian moon pulling on the other."
Curiosity didn’t stop there though. Its Navcam instrument imaged the sunset eclipse, the darkening of the skies, from Mars’ surface as Phobos passed in front of the Sun, on March 25 (Sol 2358).
The sequence has been contrast-enhanced and sped up by a factor of four. NASA/JPL-Caltech
As did NASA’s InSight lander.
As Lemmon points out, these events help make Mars relatable. "Eclipses, sunrises and sunsets and weather phenomena all make Mars real to people, as a world both like and unlike what they see outside, not just a subject in a book."