July 3, 2020
Updated on July 5, 2020 4h19
A solar eclipse seen from… Mars !
24 PER SECOND / It is not only on Earth, solar eclipses occur. In fact, many planets have more than one moon have eclipses more frequent as we do. But they are not the same paces here…
NASA / JPL
The video above, recorded by the american probe Curiosity (which was really the proverbial “right place at the right time”) date of the project is already six years old, but it has surfaced in recent days on social networks. It shows the martian moon Phobos pass in front of the sun… which allows you to note two interesting things.
The first is that Phobos is not spherical, such as “our” Moon, having rather the form of a “patatoïdes”, so say the astronomers. This can be explained by the fact that it is very small : about 27 kilometres in diameter, in its axis the longest, whereas it takes around 1000 miles for that a space object becomes spherical under its own gravity. (Although this can vary a lot with density, but that is another story : for the densities of the planets, moons and asteroids, it is about 1000 km.)
The second is that it shows the “chance” that we, on Earth, to have a Moon that is just the right size and orbiting at just the right distance to have an apparent diameter (not the “true” diameter, but that which is perceived from here) is almost identical to that of the Sun. This gives the solar eclipses of the Earth on one side much more dramatic and spectacular than a simple “stone” that did not veil that a relatively small part of the Sun.
It should be noted in this regard that Curiosity has filmed two other solar eclipses last year by Phobos and the other Deimos, which is the second natural satellite of Mars. Gold as Deimos is smaller (15 km in its widest point) and orbit much further away (about 23 000 km against 9500 km for Phobos), its eclipses are much more “discrete”, as shown in this photo :