Solar eclipses draw a lot of attention here on Earth because they are more rare phenomena. But have you ever thought how they occur on other planets? Mars, for example, has two natural satellites – Phobos and Deimos -, allowing for a much higher incidence of these events. Another detail is that, in just one day, Fobos makes 3 turns around the equatorial region of the Red Planet.
Because it has smaller satellites, Mars never has total solar eclipse, only annular or partial. Phobos, for example, has an average diameter of 11 km, well below the 1,700 km of the Moon. This satellite has a very large orbital speed, so the eclipses it causes last for a few seconds. The Mars InSight probe was able to capture one of these moments and reveal curious details of the phenomenon.
The seismometer on the probe noticed an almost imperceptible slope. The instrument is used to monitor possible earthquakes on Martian soil. On Earth, eclipses generate several changes, such as temperature declines and gusts of wind as the shadow reaches a certain region.
Mars InSight instruments did not notice changes in wind or temperature. Only the solar cells registered the transit of Phobos, which blocks about 40% of the sunlight. With that, there was a decrease in the creation of energy, which can be measured by the equipment – until then, however, these are expected results.
The seismometer issue called attention due to the minuscule alteration in its alignment. She was observed at least 3 times, excluding the possibility of a false positive. In comparison with other seismic activities, there was no similarity.
Scientists believe that a change in soil temperature may have influenced this movement of the device. During the slower passage of Phobos, there was a slight drop in temperature, registered by an infrared radiometer. Then, the soil took about 1 and a half minutes to return to the previous temperature. The deformation caused by the contraction and expansion of the soil must have influenced the instrument.
This kind of situation had happened before, by chance, here on Earth. At an observatory in Germany in 1997, a technician forgot the light on when he left the study area of the seismometer, creating noise in the analyzed data. After a while of research, it was noticed that the heat of the lamp affected the concrete in which the equipment was. With that in mind, the scientists recreated the scenario with Mars Insight data and reproduced the tilt noted on our neighboring planet.
Understanding more details of Phobos has been one of the scientists’ goals. Its orbit is decreasing at a rate of 1.8 cm per year, closer and closer to Mars. Eventually, it will disintegrate, creating a ring of debris around the planet. Understanding this phenomenon will provide other answers, such as the planet’s internal temperature and its formation.