(ORDO NEWS) — From time to time there is a reminder that our planet is indeed unusual in many amazing ways. These reminders don’t even have to come from afar – they can be very close, like our neighbor’s.
Like Earth, Mars experiences moments when its moons cast shadows on its surface. But the “eclipses” on Mars captured by NASA‘s Opportunity, Curiosity and now Perseverance rovers are very different from those on Earth.
Mars’ moons Phobos (“fear” in ancient Greek) and Deimos (“horror”) revolve around Mars every 7.65 and 30.35 hours, respectively, which is a relative instant compared to the Earth’s moon‘s 27-day orbit.
They are also much smaller than the Moon and much more bumpy – little moons rather than the beautiful round disk we see so bright in our night sky.
Technically, these events are not eclipses in our sense, but are transits that never completely cover the light of the Sun.
When the bumpy moons of Mars pass between the Sun and observers on the Martian surface, they don’t cover the star as completely as the Moon does here on Earth.
See an example of a transit observed by Perseverance in the video below.
It is easy to imagine the Sun as a giant eyeball with an unusual pupil watching something invisible to an observer on the surface.
If we discard bizarre ideas, scientists have observed a strange effect on the planet when the shadow of Phobos passes.
The Mars InSight observatory, designed to measure seismic activity, tilts slightly during these events.
Scientists attribute this slight tilt to the deformation of the surface of Mars as a result of a slight cooling effect from the decrease in solar radiation.
Of the two moons, Phobos has the larger silhouette, blocking up to 40 percent of the light from the Sun even when completely absorbed by the glare. Farther away and smaller, Deimos blocks out much less light, highlighting how incredibly special our planet is.
During a total solar eclipse on Earth, the disk of the Moon completely covers the disk of the Sun, despite the fact that the Moon is much smaller.
This is due to a very interesting coincidence. The Moon is about 400 times smaller than the Sun. It is also 400 times closer to Earth than the Sun. This means that the Sun and Moon appear to be about the same size in our sky.
True, they vary slightly, since neither the Earth’s orbit around the Sun nor the Moon’s orbit around the Earth are perfectly round.
Therefore, their sizes may appear slightly larger or smaller, depending on the position of the orbits.
This is how annular eclipses occur when the Moon does not completely cover the Sun, leaving a ring of light around the disk of the Moon.
More interestingly, the appearance of our species seems to have happened just in time to admire such perfect eclipses.
The moon began its life much closer to Earth and is currently moving away from it at a rate of about 3.82 centimeters (1.5 inches) per year. In about 600 million years, total solar eclipses will become impossible.
The video below shows Curiosity’s data on the “eclipse” of Deimos.
Observing solar eclipses from Earth can teach us interesting things about the Sun (and provided a critical test of general relativity over 100 years ago).
On Mars, scientists can also use eclipses to gain new knowledge. They can link the motion of Phobos to its gravitational pull on Mars and use this information to understand the mysterious Martian interior.
Not to mention predicting the ultimate fate of Phobos. The moon is getting closer and closer to Mars, and one day it will be so close that the gravity of Mars will pull it apart. Then, according to scientists, a ring of Phobos’ intestines will temporarily appear on the red planet.
Tracking Phobos and Deimos across the Martian sky could provide more data to help map and predict this cruel fate.
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