Solar eclipses are a wondrous thing to behold here on Earth, but witnessing an eclipse on another planet imbues the astronomical event with an even deeper air of mystery and fascination. While human eyes can only vicariously experience the sight of an alien solar eclipse, some space travelers do boast the privilege of beholding such splendors. These are the robotic probes sent by humanity to explore the alien realms that have, for now, remained intangible to astronauts.
Take, for instance, Mars. The red planet is currently the only alien world in our solar system inhabited entirely by robots. Among them is the intrepid Curiosity rover, a resilient car-sized robot that has had quite a few opportunities of observing a solar eclipse on Mars in the nearly seven years that it has spent trekking the dusty martian ground.
The most recent of these chances presented itself last month, when Curiosity was able to spot not just one, but two solar eclipses on the red planet – each produced by one of the two martian moons, Phobos and Deimos.
When the rover first landed on Mars in August of 2012, “it brought along eclipse glasses,” explains NASA, referring to the solar filters installed on Curiosity’s Mast Camera (Mastcam) and which allow the robot “to stare directly at the sun.” Thanks to these two instruments, the robot has been able to peer at the shining orb of the sun without being blinded by its glare – and to spot the two martian moons as they passed in front of our star, blotting out its light.
In late March, Curiosity’s solar filters helped the robot capture a stunning solar eclipse created by Phobos. The rover photographed the seven-mile-wide moon – the larger of the two – as it crossed in front of the sun on March 26, or Sol 2359 of the Curiosity Mars mission.
As NASA points out, the images snapped by Curiosity depicted an annular eclipse, given that Phobos didn’t completely cover the sun.
Several days before that, on March 17 (Sol 2350), the six-wheeled robot cast its inquisitive eyes on the sky overhead and observed yet another eclipse – this time produced by the smaller of the two martian moons, the 1.5-mile-wide Deimos.
“Because Deimos is so small compared to the disk of the sun, scientists would say it’s transiting the sun,” note NASA officials.
While the rover’s Mastcam was busy recording the eclipses unfolding in the sky, another one of Curiosity’s cameras had its eye fixed on the ground. As such, it managed to capture the shadow of Phobos as the moon passed over the robot on March 25 (Sol 2358), causing a dip in the light coming from the setting sun.
When I dip you dip we dip.— Curiosity Rover (@MarsCuriosity) April 4, 2019
This dip in post-sunset light was caused by Phobos. The Martian moon was rising as the sun set, casting an elongated shadow. Dust in the atmosphere acted like a screen, across which the shadow was projected. https://t.co/pzPVOPdLZ9 pic.twitter.com/De5aFokdOk
Aside from being glorious to behold, spotting and analyzing solar eclipses on Mars has helped scientists learn a great deal about the two martian moons, states NASA.
“Besides being cool — who doesn’t love an eclipse? — these events also serve a scientific purpose, helping researchers fine-tune their understanding of each moon’s orbit around Mars.”
According to Mark Lemmon, a scientist at Texas A&M University, and a co-investigator with Curiosity’s Mastcam, each new eclipse observation helps “pin down the details of each orbit.”
This is important because the two martian moons orbit their planet a lot closer than our moon circles the Earth. Phobos whips around Mars three times a day, whereas the more distant Deimos goes around the red planet once every 30 hours.
“Those orbits change all the time in response to the gravitational pull of Mars, Jupiter or even each Martian moon pulling on the other.”
The latest eclipse sightings by Curiosity come just a few short days after another one of NASA’s Mars probes, the InSight Lander, caught sight of the shadow of a martian solar eclipse produced by Phobos, as reported by The Inquisitr in mid-March.