Every once in a while, we are reminded that our planet is truly extraordinary in many wonderful ways. These reminders don’t have to come from far away, they can be as close as your next door neighbor.
Like Earth, Mars experiences moments when a satellite casts a shadow on its surface. But the Mars eclipses captured by NASA’s Opportunity, Curiosity (embedded below), and now Perseverance rovers are very different from Earth’s.
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Mars’ moons Phobos (ancient Greek for “terror”) and Deimos (“terror”) orbit Mars in 7.65 and 30.35 hours, respectively, a relative time compared to Earth’s moon’s 27-day revolution. It’s a blink of an eye.
They’re also much smaller than the moon, and rather than the beautiful round discs we see shining so sharply in the night sky, they’re rather lumpy little moontates.
Strictly speaking, these phenomena are not solar eclipses like we experience, but rather transits that do not completely block the sun’s light. When Mars’ rugged moonlets pass between the sun and observers on Mars’ surface, they don’t completely cover the star like the moon does on Earth.
See examples of transits seen by Perseverance in the video below.
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It’s not hard to imagine the sun as a giant eyeball with a unique pupil that tracks something invisible to surface-bound observers.
Fantastic concepts aside, scientists have observed strange effects on Earth with the passage of Phobos’ shadow. The Mars Insight lander, an observatory designed to measure seismic activity, tilts slightly during these events. Scientists believe that this slight tilt is due to deformation of the surface of Mars as a result of a very slight cooling effect due to reduced solar radiation.
Of the two moons, Phobos has a larger silhouette and blocks as much as 40 percent of the sun’s light even when completely engulfed by glare. Deimos is much more distant and smaller, blocking much less light and highlighting how incredibly special our planet is.
When a total solar eclipse occurs on Earth, the moon’s disk completely covers the sun’s disk, even though the moon is much smaller.
This is a very interesting coincidence. The moon is about 1/400th the size of the sun. It is also about 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.
This is a little different because neither the Earth’s orbit around the Sun nor the Moon’s orbit around the Earth are perfectly circular. Therefore, depending on its orbital position, its size may appear slightly larger or smaller. This results in an annular solar eclipse, where the moon does not completely cover the sun, leaving a ring of light around the moon’s disk.
Even more interestingly, the emergence of our species seems to have happened at just the right time to marvel at such a perfect solar eclipse. The Moon was born much closer to Earth and is now moving away from us at a rate of about 3.82 centimeters (1.5 inches) per year.please give me another one About 600 million yearsTherefore, a total solar eclipse will be impossible.
The video below shows Curiosity data from the Deimos “Solar Eclipse.”
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Observing solar eclipses from Earth tells us amazing things about the Sun (and made possible an important test of general relativity more than 100 years ago).
On Mars, scientists can also use solar eclipses to learn things. They can link Phobos’ movements to its gravitational influence on Mars and use that information to understand Mars’ mysterious interior.
Needless to say, it predicts the ultimate fate of Phobos. The Moon is gradually moving closer to Mars and will one day grow so close that Mars’ gravity will pull it apart. After that, scientists think the red planet will temporarily have the intestinal ring of Phobos.
Tracking Phobos and Deimos across the Martian sky could yield more data to help map and predict this violent fate.
A version of this article was first published in August 2022.
