Eclipse observed on Mars.

NASA's Perseverance Rover has observed an eclipse from the surface of Mars, caused by the moon Phobos passing in front of the Sun. Phobos is significantly smaller than our Moon, only 17 km in diameter compared to 3475 km, but orbits much closer to Mars than the Moon does to Earth, an average of 9376 km compared to 384 400 km, which combined with the smaller apparent size of the Sun seen from Mars, which is roughly 1½ times as far from the Sun as the Earth is, means that eclipses are still an observable phenomenon. 

Solar eclipse on Mars, caused by the moon Phobos passing in front of the Sun, recorded by the Perseverance Rover. Images are at 10 second intervals, with the whole event lasting much less time than an eclipse on Earth, due to the closer orbit of Phobos, and the correspondingly higher speed of the Martian moon, which takes only 7.6 hours to orbit the planet. NASA.

The eclipse, which occurred on 30 September 2024, was the second such eclipse observed by Perseverance this year, with the Curiosity and Opportunity rovers also having Martian eclipses. These eclipses are common because, unlike that of our Moon, the orbit of Phobos has very little tilt, effectively remaining above the planet's equator at all times.

An eclipse caused by the passage of Phobos in front of the Sun recorded by the Perseverance Rover on 8 February 2024. NASA.

Mars's second moon, Deimos, does not cause such obvious eclipses, as it is only 6.2 km in diameter, and orbits at an altitude of 23 460 km, making it almost invisible from the planet's surface.

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Fobos-Grunt crashes into the Pacific Ocean.

Fobos-Grunt was the most ambitious planetary probe ever launched by the Russian Space Agency (or anyone else on Earth for that matter), intended to travel to the larger moon of Mars, Phobos, and return to Earth with samples. Had it succeeded it would have been only the second probe to land on a satellite of another planet (after the European Space Agency's Huygens Probe, which landed on Saturn's moon Titan) and the only probe ever to have reached the orbit of another planet as returned home with samples (NASA's Stardust Probe previously managed to return samples from comet Wild 2).

A full-scale replica of the Fobos-Grunt Probe.

The probe also carried the Yinghuo-1 orbiter on behalf of the Chinese Space Administration, China's first attempt to send a mission to another planet, intended to orbit Mars for about two years, studying the planets atmosphere, ionosphere and magnetic field. In addition it carried the Living Interplanetary Flight Experiment on behalf of the Planetary Society, an experiment to see how colonies of micro-organisms would survive the journey to Mars and back.

Unfortunately the Fobos-Grunt Probe ran into trouble during its launch on 9 November 2011, failed to reach the correct hight for the probe to separate from the launcher and head for Mars, and has been in an unstable, declining orbit ever since. The probe is thought to have finally crashed into the Pacific Ocean on Sunday 15 January 2012, at approximately 5.45 pm GMT, somewhere over a thousand kilometers to the west of southern Chile. It is thought that most of the 13 tonne probe will have burned up on re-entry, but something like 200-300 kg of tougher components will probably have reached the sea.

There have been strong recriminations in Russia, a country that has suffered a string of space accidents in the last year, with accusations of sabotage and the announcement of a new investigation into the incident by Russian Deputy Prime Minister Dmitry Rogozin. There has also been a degree of disparagement from sources outside of Russia (mostly from people who have never launched a Mars probe for themselves). In the light of which it is easy to lose sight of how ambitious the original probe was. It it is unfortunate that the mission was let down by a launch vehicle, but the planning of the mission and building of the probe reflects a considerable achievement in itself, and it is unlikely that this will be the last interplanetary probe to come out of Russia.

See also Russian satellite crashes into house, Mysterious object falls from the sky in Namibia, Space age archaeology, NASA sets its sights on Gale Crater and Mars on Sciency Thoughts YouTube.

The surface of Vesta.

A week after NASA/JPL's Dawn Space Probe moved into orbit around the asteroid Vesta images of the hole of the surface have been released. Vesta is the second largest object in the Asteroid Belt and has a surface area of 883 000 km², twice that of California or 42 times that of Wales. It shows considerable variation over its surface.

Animation of the Surface of Vesta.

There is a higher resolution version on the Dawn website here.

Much of the south of the asteroid is smooth, while northern part of Vesta is heavily pitted, the result of many small impacts. This implies the northern surface is older than the southern; the most likely scenario is that both hemispheres were pitted heavily by impacts early in the solar system's history (though still over a very long period of time), and that the southern hemisphere was then resurfaced by a single large impact.

Overlapping craters nicknamed 'The Snowman'

in the Northern Hemisphere of Vesta.

The equatorial region of Vesta show heavy grooving, which is unexpected. Similar grooves are also seen on the Martian moon, Phobos, where they are attributed to repeated impacts by debris in the same orbit as the moon, repeatedly striking from the same direction. The Russian Phobos-Grunt mission is due to visit the moon and collect samples in 2013, which should vastly improve our understanding of Phobos' history.

Grooves on the surface of Phobos.

This is surprising on Vesta as it occupies a more sparse area of space; our current understanding implies the Asteroid Belt to be made up of scattered, remote objects. The grooving implies that early in the Solar System's history the Asteroid Belt may have been more densely packed.

The Dawn Probe should remain in orbit about Vesta for a year, during which time it should gather considerable information about the asteroid's structure and mineralogy. After this it will move on to Ceres, the largest object in the Asteroid Belt.

See also Visiting Vesta, 2010 TK₇, Earth's Trojan Asteroid and Asteroid 2011MD.