How did the equatorial ridge on Saturn's moon Iapetus form?

Apr 01, 2012
Raw image from Cassini space probe of the equatorial ridge on Saturn's moon Iapetus. Image: NASA

Saturn's moon Iapetus is one of the most unusual moons in our solar system.

Perhaps the most bizarre feature of is its equatorial ridge, a 20-km (12.4- mi) high, 200-km (124-mi) wide mountain range that runs exactly along the , circling more than 75 percent of the moon.

No other body in the solar system exhibits such a feature, and as Dombard et al. show, previous models have been unable to adequately explain how the ridge formed.

The authors now propose that the ridge formed from an ancient giant impact that produced a subsatellite around Iapetus.

Tidal interactions with Iapetus ultimately led to orbital decay, eventually bringing the subsatellite close enough that the same forces tore it apart, forming a debris ring around Iapetus.

Material from this ring then rained down on Iapetus, creating the mountain ring along the equator.

Explore further: Rosetta Comet Landing in 'Thud' and 3D

More information: Delayed formation of the equatorial ridge on Iapetus from a subsatellite created in a giant impact, Journal of Geophysical Research-Planets, doi:10.1029/2011JE004010 , 2012.

add to favorites email to friend print save as pdf

Related Stories

How Iapetus got its ridge

Dec 13, 2010

For centuries, people wondered how the leopard got its spots. The consensus is pretty solid that evolution played a major role.

Cassini Prepares to Fly by Walnut-Shaped Moon

Sep 06, 2007

Cassini will make its only close flyby of Saturn's odd, two-toned, walnut-shaped moon Iapetus on Sept. 10, 2007, at about 1,640 kilometers (1,000 miles) from the surface.

Saturn's Old Moon Iapetus Retains Its Youthful Figure

Jul 17, 2007

Saturn's distinctive moon Iapetus (eye-APP-eh-tuss) is cryogenically frozen in the equivalent of its teenage years. The moon has retained the youthful figure and bulging waistline it sported more than three ...

Cassini Gets Close-Up Views of Saturn's Moon Iapetus

Sep 12, 2007

Cassini completed its closest flyby of the odd moon Iapetus on Sept. 10, 2007. The spacecraft flew about 1,640 kilometers (1,000 miles) from Iapetus' surface and is returning amazing views of the bizarre moon. ...

Saturn's Icy Moon Iapetus

Jan 04, 2005

NASA's Cassini spacecraft successfully flew by Saturn's moon Iapetus at a distance of 123,400 kilometers (76,700 miles) on Friday, Dec. 31. NASA's Deep Space Network tracking station in Goldstone, Calif., received ...

Recommended for you

Rosetta Comet Landing in 'Thud' and 3D

3 hours ago

(Phys.org) —A 3D image shows what it would look like to fly over the surface of comet 67P/Churyumov-Gerasimenko. The image was generated from data collected by the Rosetta Lander Imaging System (ROLIS) ...

Time in space exposes materials to the test of time

8 hours ago

Much like that pickup truck rusting in your backyard thanks to time, rain and the elements, extended stays in the brutal environment of space can take its toll on spacecraft, satellites and space stations. ...

Earth's orbit around the sun

10 hours ago

Ever since the 16th century when Nicolaus Copernicus demonstrated that the Earth revolved around in the Sun, scientists have worked tirelessly to understand the relationship in mathematical terms. If this ...

How can we search for life on icy moons such as Europa?

10 hours ago

Our solar system is host to a wealth of icy worlds that may have water beneath the surface. The Cassini spacecraft recently uncovered evidence of a possible ocean under the surface of Saturn's moon, Mimas.

CubeSat instruments to demonstrate NASA firsts

11 hours ago

The Dellingr six-unit CubeSat, which is taking its developers just one year to design, build and integrate, won't be the only potentially groundbreaking capability for NASA. Its heliophysics payloads also ...

User comments : 11

Adjust slider to filter visible comments by rank

Display comments: newest first

kevinrtrs
1.6 / 5 (12) Apr 02, 2012
The authors now propose that the ridge formed from an ancient giant impact that produced a subsatellite around Iapetus.

Whenever there's no naturalistic explanation for any mysterious feature, the magical "giant impact" cause is invoked.

Note how this applies to Mercury's dense core, the formation of the moon, the disappearance of water from Mars, Uranus rolling along in it's orbit, the incredible gouging of Miranda, the supposed extinction cause of Dinosaurs etc. I've probably left out half a dozen or more of such "explanations".

Where is the REAL science behind this kind of explanation? These invocations are ALL unobserved and with zero convincing evidence, bar none.

Spaceman78
3 / 5 (2) Apr 02, 2012
How does the Universe form such magnificent structures following it's own laws. Incredible........and a mystery.
Travis_Grae_Hassig
not rated yet Apr 02, 2012
Obviously an ancient race of advanced aliens...
Teneca
5 / 5 (1) Apr 02, 2012
Incredible........and a mystery
It's apparently recycled research too. The impact theory of Lapetus ridge is researched notoriously (1, 2) and I can't see any progress with it from the above article.
El_Nose
3 / 5 (2) Apr 02, 2012
@kev great examples except the water on mars -- that one is cause Mars has no magnetosphere
Pyle
5 / 5 (3) Apr 02, 2012
Ummm, I usually just ignore kevin but, isn't a celestial impact a "naturalistic explanation"? I believe we observe impacts almost nightly, i.e. "shooting stars". What is magical about rocks running into other rocks?

Oh, and Nose, please don't give even the appearance of encouragement to hit and run theists.
Vendicar_Decarian
5 / 5 (1) Apr 02, 2012
The ridge is formed from a collection of ring material that has been swept up by the moon.

It is patently obvious.
bewertow
2.3 / 5 (3) Apr 03, 2012
The authors now propose that the ridge formed from an ancient giant impact that produced a subsatellite around Iapetus.

Whenever there's no naturalistic explanation for any mysterious feature, the magical "giant impact" cause is invoked.

Note how this applies to Mercury's dense core, the formation of the moon, the disappearance of water from Mars, Uranus rolling along in it's orbit, the incredible gouging of Miranda, the supposed extinction cause of Dinosaurs etc. I've probably left out half a dozen or more of such "explanations".

Where is the REAL science behind this kind of explanation? These invocations are ALL unobserved and with zero convincing evidence, bar none.



...and whenever a natural explanation is provided kevintrs shouts "Hurr durr a zombie wizard who is his own father did it!"
Estevan57
2 / 5 (28) Apr 03, 2012
Space gophers did it. April fools.
El_Nose
5 / 5 (1) Apr 15, 2012
@Pyle

i will respond to whom ever i like, I am a theist. But that does not discredit the fact Mars has no magnetosphere.. and the fact that Kevin made very good points except one.

If you don;t like trolls - then don;t act like one yourself, His argument not mention God, unfortunately i cannot say the same for yours.
Pyle
1 / 5 (1) Apr 16, 2012
Nose:

No, Kevin didn't make very good points. He made a ridiculous statement, that impacts are "magical". He then listed several observations that have been made and appear to be the result of impacts. Impacts are not magical and are in fact common place. Our understanding of physics; observations of the solar system; and our theories of its creation/development strongly suggest that impacts between larger bodies in the solar system occurred.

I don't like to see inflammatory comments stand without pointing out the absurdity of them and, further, exposing the underlying motivation to attack science seemed only fair considering his past behavior. The fact that he didn't mention His Noodly Appendage was the biggest reason I did, to identify him for what he is: a religious troll attacking science. I'd prefer being labelled a troll for my unmotivated attacks instead of when I rise to the call.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.