Images provided by NASA's Cassini spacecraft in 2005 reveal an almost straight-line equatorial mountain range that towers upwards of 12 miles and spreads as wide as 60 miles, encircling more than 75 percent of Iapetus, the ringed planet's third-largest moon, and causing it to resemble a walnut.
"There's nothing else like it in the solar system," said Andrew Dombard, associate professor of earth and environmental sciences at the University of Illinois at Chicago. "It's something we've never seen before and didn't expect to see."
Some scientists have hypothesized that Iapetus's mountains were formed by internal forces such as volcanism, but Dombard, along with Andrew Cheng, chief scientist in the space department at the Johns Hopkins University Applied Physics Laboratory, William McKinnon, professor of earth and planetary sciences at Washington University in St. Louis and Jonathan Kay, a UIC graduate student studying with Dombard, think the mountains resulted from icy debris raining down from a sub-satellite or mini-moon orbiting Iapetus, which burst into bits under tidal forces of the larger moon.
"Imagine all of these particles coming down horizontally across the equatorial surface at about 400 meters per second -- the speed of a rifle bullet, one after another, like frozen baseballs," said McKinnon. "At first the debris would have made holes to form a groove that eventually filled up."
Dombard and his collaborators think the phenomenon is the result of what planetary scientists call a giant impact, where crashing and coalescing debris during the solar system's formation more than 4 billion years ago created satellites such as the Earth's Moon and Pluto's largest satellite Charon.
They've done a preliminary analysis demonstrating the plausibility of impact formation and subsequent evolution of Iapetus's sub-satellite. Dombard said Iapetus is the solar system's moon with the largest "hill sphere" -- the zone surrounding a moon where the gravitational force is stronger than that of the planet it circles.
"It is the only moon far enough from its planet, and large enough relative to its planet, that a giant impact may be able to form a sub-satellite," said Cheng.
This lends plausibility to the rain of debris along the equator hypothesis, Dombard said, but he adds that more sophisticated computer modeling and analysis is planned in the coming years to back it up.
Other explanations have been proposed by scientists as to what caused this odd formation of mountains on Iapetus, but Dombard said they all have shortcomings.
"There are three critical observations that you need to explain," he said. "Why the mountains sit on the equator, why it's found only on the equator, and why only on Iapetus? Previous models address maybe one or two of those critical observations. We think we can explain all three."
The planetary scientists will present details of their model Dec. 15 at the American Geophysical Union's fall meeting in San Francisco.Paul Francuch
Paul Francuch | Newswise Science News
Mars 2020 mission to use smart methods to seek signs of past life
17.08.2017 | Goldschmidt Conference
Gold shines through properties of nano biosensors
17.08.2017 | American Institute of Physics
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
17.08.2017 | Physics and Astronomy
17.08.2017 | Earth Sciences
17.08.2017 | Physics and Astronomy