Scientists around the world now view the study of comets as an important step in trying to understand the history of our solar system. In November 2014, on the comet Churyumov-Gerasimenko, separated from the Rosetta probe, the Philae module landed - it became the first spacecraft to make a soft landing on the comet.
However, in the case of astronauts landing on a comet, what would they experience?
In recent decades, NASA and other space agencies have launched several missions to explore comets, so astronauts would certainly have the necessary knowledge of heavenly wanderers.
For example, in March 1986 the ESA automatic interplanetary station "Giotto" flew at a distance of 596 km from the nucleus of Halley's comet, having received damage from its particles, and in July 1992, the apparatus met with the comet Grigg-Skjellerup - it flew from it at a distance of about 200 km.
In January 2004, NASA's Stardust spacecraft passed 240 km from Comet Wild 2 - images of the comet's surface were taken, and samples of matter from its tail were collected. A capsule with cometary matter was delivered to Earth 2 years later.
The photographs taken during the missions showed that comet nuclei are small in size - from one to several tens of kilometers, and some of them have an irregular shape. Altea Moorehead, a researcher at the George Marshall Space Flight Center, noted that the irregular shape could be caused by low gravity and added that for this reason "it would be strange to live on a comet."
On spherical bodies like Earth, gravity is directed vertically downward, however, if you are on a comet shaped like a dumbbell, gravity can pull downward or to the side, depending on location.
However, the force of gravity would be felt weak, for example, the gravity of Halley's comet is approximately equal to the gravity of Everest, if the mountain were placed in space - an object thrown down from the chest would fall to the ground for 2 minutes. If on Earth you would have jumped 20 cm up, then on Halley's comet the same effort could throw you off a celestial body.
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Of course, comets, especially irregular ones, can offer many objects for study, for example, craters and cracks, but the entire surface area of such a celestial body as Halley's comet is approximately equal to the area of Lanai Island in Hawaii (364 square kilometers). Comets are known for the cloud of dust and gas that surrounds the core.
This cloud (coma) forms when ice on the surface of a comet turns into gas. On Halley's comet, this happens when it is at a distance of about 3 astronomical units from the Sun (about 150 million km). It has a coma for only 1 year out of 76 years during which it makes a circle around the Sun.
Moorehead noted that if a person were on a comet at this time, the cloud would most likely eclipse the stars, and during the day (on Halley's comet - from 2.2 to 7.4 Earth days), the field of view would be filled with diffused light - as if you are standing in a thick fog.
The orbits of many comets are elliptical, thanks to which the comet can visit the Kuiper belt (the region of the solar system beyond the orbit of Neptune) and in the inner part of the solar system. Due to the elliptical orbit, surface temperatures can vary greatly depending on where the comet is.
When Giotto visited Halley's comet in 1986, it was 0.9 astronomical units from the Sun and its surface temperature was 77 degrees. "Rosetta" in July 2014 recorded on the surface of the comet Churyumov - Gerasimenko minus 70 degrees - then the comet was at a distance of more than 3 astronomical units (450 million km) from the Sun.
The elongated orbits will also cause the time taken to make a call to Earth vary from minutes to hours.