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Archive for September 15th, 2009

Jupiter’s ‘Protective Role’ Revisited

Posted by feww on September 15, 2009

How Jupiter may be defending Earth against catastrophic collisions

In Jupiter Bombarded

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 full profile
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 red spot
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


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

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.]

: 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!

Related Links:

Posted in Comet 111P, Helin-Roman-Crockett, planetary tidal effects, Shoemaker-Levy 9, temporary satellite capture | Tagged: , , , , , , , , , , , , | 2 Comments »

El Niño Update [14 Sept 2009]

Posted by feww on September 15, 2009

ENSO Cycle: Recent Evolution, Current Status and Predictions

The following UPDATE is prepared by

Climate Prediction Center / NCEP – 14 Sept 2009

The latest weekly SST departures are:

  • Niño 4   ~ 0.8ºC
  • Niño 3.4  ~ 0.9ºC
  • Niño 3 ~ 0.8ºC
  • Niño 1+2 ~ 0.5ºC

El Niño Map.
[SOURCE: NOAA/ Climate Prediction Center / NCEP]

Niño Region SST Departures (ºC) –  Recent Evolution
SST anom 14-sept-09

Weekly SST Departures (ºC) for the Last Four Weeks

  • During the last four weeks, SST anomalies have increased in some areas of the equatorial Pacific Ocean.
  • During the last month, the change in equatorial SST

Central & Eastern Pacific Upper-Ocean (0-300 m) Weekly Heat Content Anomalies
Since April 2009, the upper-ocean heat content has been above average across the eastern half of the equatorial Pacific Ocean. The heat content was previously below-average from mid-August 2008 through March 2009, with a minimum reached in late December 2008.

Weekly Heat Content Evolution in the Equatorial Pacific

EQ Upper-Ocean Heat anoms  -14sept09

1. During September 2008 –January 2009, negative heat content anomalies returned and then strengthened in the central and eastern equatorial Pacific as La Niña conditions redeveloped.

2. The negative anomalies weakened during January-March 2009, with anomalies becoming positive since late March.

In April 2009, the combined effects of an oceanic Kelvin wave and weaker easterly trade winds contributed to an increase in the upper-ocean heat content anomalies across the Pacific Ocean.

Since April 2009, heat content anomalies have remained above-average.

3. Recently, the downwelling phase of a Kelvin wave has shifted eastward.

    Oceanic Kelvin waves have alternating warm and cold phases. The warm phase is indicated by dashed lines. Down-welling and warming occur in the leading portion of a Kelvin wave, and up-welling and cooling occur in the trailing portion.

    SST Outlook: NCEP CFS Forecast Issued 13 September 2009
    El Niño will last through Northern Hemisphere winter 2009-10.


    • El Niño is present across the equatorial Pacific Ocean.
    • Sea surface temperatures (SST) remain +0.5 to +1.5ºC above-average across much of the equatorial Pacific Ocean.
    • Based on current observations and dynamical model forecasts, El Niño is expected to strengthen and last through Northern Hemisphere winter 2009-10.

    Information and images on this page are sourced from Climate Prediction Center/NCEP/NOAA.

    For additional information see following links.

    Relate Links:

    El Niño Updates

    Posted in Climate Prediction, El Niño weekly report, equatorial Pacific Ocean, Global SST anomalies, Oceanic Kelvin waves | Tagged: , , , , , , | 3 Comments »