Sun, 27 Nov 2022 Today's Paper

Comets left their mark on Jovian moons

26 January 2010 02:37 am - 0     - {{hitsCtrl.values.hits}}

A A A



The differing appearance of Jupiter's two largest moons, Callisto and Ganymede, may be due to the number and speed of comets hitting them early in their evolution, say US researchers.
Ganymede and Callisto are similar in size and are made of a similar mixture of ice and rock, but data from the Galileo and Voyager spacecraft show that they look different at the surface and on the inside.

Explaining why these two moons are different has eluded scientists for more than 30 years ago.
Using computer modelling Dr Amy Barr and Dr Robin Canup of the Southwest Research Institute believe the two moons diverged in their evolutionary paths about 3.8 billion years ago, during the Late Heavy Bombardment, a phase in the solar system's history dominated by large impact events.

The research appears today in the journal Nature Geoscience
"Impacts during this period melted Ganymede so thoroughly and deeply that the heat could not be quickly removed," says Barr. "All of Ganymede's rock sank to its centre the same way that all the chocolate chips sink to the bottom of a melted carton of ice cream."
"Callisto received fewer impacts at lower velocities and avoided complete melting."

Jupiter's attraction

In the model, Jupiter's strong gravity focuses cometary impactors onto Ganymede and Callisto. Each impact onto Ganymede or Callisto's mixed ice and rock surface creates a pool of liquid water, allowing rock in the melt pool to sink to the moon's centre.

Ganymede is closer to Jupiter and therefore is hit by twice as many icy impactors as Callisto, and the impactors hitting Ganymede have a higher average velocity.

Modelling by Barr and Canup shows that core formation begun during the late heavy bombardment becomes energetically self-sustaining in Ganymede, but not Callisto
The study sheds new light on the 'Ganymede-Callisto dichotomy,' a classical problem in comparative planetology, a field of study that seeks to explain why solar system objects with similar characteristics have radically different appearances.

"Similar to Earth and Venus, Ganymede and Callisto are twins, and understanding how they were born the same and grew up to be so different is of tremendous interest to planetary scientists," says Barr.

"Our study shows that Ganymede and Callisto record the fingerprints of the early evolution of the solar system, which is very exciting and not at all expected."

ABC


Order Gifts to Sri Lanka. See Kapruka's top selling online shopping categories such as Toys, Vegetables, Grocery, Flowers, Birthday Cakes, Fruits, Chocolates, Clothing and Electronics. Also see Kapruka's unique online services such as Sending Money,Online Books, Delivery Service, Food Delivery and over 700 top brands. Also get products from Amazon & Ebay via Kapruka Gloabal Shop Sri Lanka

  Comments - 0

Order Gifts to Sri Lanka. See Kapruka's top selling online shopping categories such as Toys, Vegetables, Grocery, Flowers, Birthday Cakes, Fruits, Chocolates, Clothing and Electronics. Also see Kapruka's unique online services such as Sending Money,Online Books, Delivery Service, Food Delivery and over 700 top brands. Also get products from Amazon & Ebay via Kapruka Gloabal Shop Sri Lanka

Add comment

Comments will be edited (grammar, spelling and slang) and authorized at the discretion of Daily Mirror online. The website also has the right not to publish selected comments.

Reply To:

Name - Reply Comment




Order Gifts to Sri Lanka. See Kapruka's top selling online shopping categories such as Toys, Vegetables, Grocery, Flowers, Birthday Cakes, Fruits, Chocolates, Clothing and Electronics. Also see Kapruka's unique online services such as Sending Money,Online Books, Delivery Service, Food Delivery and over 700 top brands. Also get products from Amazon & Ebay via Kapruka Gloabal Shop Sri Lanka

Downfall and death of LTTE’s Mahathaya

The Liberation Tigers of Tamil Eelam (LTTE) ceased to exist as a functioning

Rishi Sunak; why SL did not have a Tamil or Muslim as President?

Britain now has a British Asian, Hindu Prime Minister, though Rishi Sunak is

How and why MGR launched ADMK 50 years ago

17 October 1972 was a Tuesday. Fifty years ago on that auspicious day, a new

Amitabh Bachchan: Evergreen Emperor of Hindi cinema turns 80

Well-known Hindi film actor Amitabh Bachchan celebrated his eightieth birthda