How Jupiter may be defending Earth against catastrophic collisions
FEWW said:
Jupiter, the “biggest guy at the door,” as if functioning as a major part of the solar system’s “defense labyrinth,” protecting the inner planets, took a massive pounding from an asteroid or comet, which left a dark bruise the size of Pacific Ocean [and growing.]
Jupiter: Image taken by Hubble Space Telescope in 2006. credit ESA/NASA/Hubble Team
It’s now transpired that Jupiter captured Comet 147P/Kushida-Muramatsu as a “temporary moon” locking the comet in an irregular orbit for about 12 years (between 1949 and 1961).
Jupiter’s Great Red Spot — This Voyager 1 picture of the great red spot shows a white oval with its “wake” of counter-rotating vortices. North is at the top and the distance from top to bottom is about 24,000 km. This enhanced color view emphasizes red and blue at the expense of green. Note the puffy features inside the GRS, and the “reverse-S” spirals inside both the GRS and the oval. The large white feature extending over the northern part of the GRS was observed to revolve about the GRS center with a period of 6 days.
[Voyager 1-98 – P-21431C – June 6, 1979] Image and Caption: NASA
The following is a Press Release issued by the EUROPEAN PLANETARY SCIENCE CONGRESS 2009
JUPITER CAPTURED COMET FOR 12 YEARS IN MID-20TH CENTURY
Comet 147P/Kushida-Muramatsu was captured as a temporary moon of Jupiter in the mid-20th century and remained trapped in an irregular orbit for about twelve years.
There are only a handful of known comets where this phenomenon of temporary satellite capture has occurred and the capture duration in the case of Kushida-Muramatsu, which orbited Jupiter between 1949 and 1961, is the third longest. The discovery will be presented at the European Planetary Science Congress in Potsdam by Dr David Asher on Monday 14 September.
“Family portrait” of the four largest moons of Jupiter
Ganymede: Natural color view of Ganymede from the Galileo spacecraft during its first encounter with the satellite. The images which combine for this color image were taken beginning at Universal Time 8:46:04 UT on June 26, 1996. [The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA’s Office of Space Science, Washington, DC.]
Europa: This image shows the approximate natural color appearance of trailing hemisphere of Jupiter’s ice-covered satellite, Europa. Europa is about 3,160 kilometers (1,950 miles) in diameter, or about the size of Earth’s moon. This image was taken on September 7, 1996, at a range of 677,000 kilometers (417,900 miles) by the solid state imaging television camera onboard the Galileo spacecraft during its second orbit around Jupiter. The image was processed by Deutsche Forschungsanstalt fuer Luft-und Raumfahrt e.V., Berlin, Germany.
IO: A full-disk color view of Jupiter’s volcanic moon Io as seen by NASA’s Galileo spacecraft camera is shown in enhanced color to highlight details of the surface, taken by Galileo in late June 1996.
Callisto: This picture of Callisto was taken by Voyager 2 from a distance of 2,318,000 kilometers (1,438,000 miles). Callisto is covered with bright spots which are meteorite impact craters. Images and caption: NASA. [Edited by FEWW]
An international team led by Dr Katsuhito Ohtsuka modelled the trajectories of 18 “quasi-Hilda comets”, objects with the potential to go through a temporary satellite capture by Jupiter that results in them either leaving or joining the “Hilda” group of objects in the asteroid belt. Most of the cases of temporary capture were flybys, where the comets did not complete a full orbit. However, Dr Ohtsuka’s team used recent observations tracking Kushida-Muramatsu over nine years to calculate hundreds of possible orbital paths for the comet over the previous century. In all scenarios, Kushida-Muramatsu completed two full revolutions of Jupiter, making it only the fifth captured orbiter to be identified.
Dr Asher said, “Our results demonstrate some of the routes taken by cometary bodies through interplanetary space that can allow them either to enter or to escape situations where they are in orbit around the planet Jupiter.”
Asteroids and comets can sometimes be distorted or fragmented by tidal effects induced by the gravitational field of a capturing planet, or may even impact with the planet. The most famous victim of both these effects was comet D/1993 F2 (Shoemaker-Levy 9), which was torn apart on passing close to Jupiter and whose fragments then collided with that planet in 1994. Previous computational studies have shown that Shoemaker-Levy 9 may well have been a quasi-Hilda comet before its capture by Jupiter.
“Fortunately for us Jupiter, as the most massive planet with the greatest gravity, sucks objects towards it more readily than other planets and we expect to observe large impacts there more often than on Earth. Comet Kushida-Muramatsu has escaped from the giant planet and will avoid the fate of Shoemaker-Levy 9 for the foreseeable future”, said Dr Asher.
The object that impacted with Jupiter this July, causing the new dark spot discovered by Australian amateur astronomer Anthony Wesley, may also have been a member of this class, even if it did not suffer tidal disruption like Shoemaker-Levy.
“Our work has become very topical again with the discovery this July of an expanding debris plume, created by the dust from the colliding object, which is the evident signature of an impact. The results of our study suggest that impacts on Jupiter and temporary satellite capture events may happen more frequently than we previously expected,” said Dr Asher.
NOT so fast! Comet Kushida-Muramatsu’s orbital path around Jupiter (credit: Ohtsuka/Asher)
The team has also confirmed a future moon of Jupiter. Comet 111P/Helin-Roman-Crockett, which has already orbited Jupiter three times between 1967 and 1985, is due to complete six laps of the giant planet between 2068 and 2086. END.
The ‘Interceptory role’ of Mars may be even more amazing!
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