The Cassini spacecraft had detected a large debris disk which appeared to be like rings around the 950-mile-wide moon Rhea. Scientists firmly believe that the discs are composed of particles ranging from the size of pebbles to big rocks.

In contrast to the rings around Jupiter, Saturn, Uranus and Neptune, the alleged arcs around Rhea remain invisible and cannot be seen directly. Scientists confirmed the existence of arcs based on the measurements made by Cassini, which detected a fall in electrons on both sides of the moon, indicating that the existence of rings was absorbing the electrons.

This is an artist concept of the ring of debris that may orbit Saturn’s second-largest moon, Rhea. The suggested disk of solid material is exaggerated in density here for clarity.

Credit: NASA/JPL/JHUAPL

It’s uncertain that when the rings would have originated, one thing is certain that they originated as a result of a collision of an asteroid or comet which took place long ago that disgorged the debris around Rhea.

“There is also possibility that rings might have formed even at the time of Rhea’s formation,” said Geraint Jones, a space physicist from University College of London.

Till now, we were known that only planets have rings, added Jones, who began the research while at the Max Planck Institute for Solar System Research in Katlenburg-Lindau, Germany.

The Cassini mission, which was a joint effort by NASA and the space agencies of Italy and Europe, was launched into space in 1997. The spacecraft reached Saturn in 2004. The mission is controlled by NASA’s Jet Propulsion Laboratory in Pasadena.

“It is the first time to detect a moon having rings around it”, said the National Aeronautics and Space Administration.

Rhea, which is having a diameter of about 1500 kilometers, is the second-largest moon of Saturn. Cassini detected alleged arcs of debris which stretches several thousand miles from end to end said NASA.

“After excluding many other possibilities, we said these discs have similarities of rings,” said Jones. “No one might have expected rings around a moon.”

Cassini is the first spacecraft to explore the Saturn system of rings and moons from orbit.

‘Until now we believed that Saturn was the only planet having rings,’ said a scientist of Cassini mission. “Now we also have a moon of Saturn which seems to be a miniature version of it even more elaborately decorated parent.”

Relevant Links:

• Saturn’s Moon Rhea Also May Have Rings
• http://www.nasa.gov/mission_pages/cassini/media/rhea20080306.html

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They said that the new technique known as microlensing is very promising and can be used for many more stars with earth like Stars revolving around them.

Scott Gaudi, who led the study, said “We discovered a new solar system that appears similar to the solar system in which we live”

Using the technique of gravitational microlensing, a network of astronomers around the world from about 11 countries spotted the system that comprises two planets that are revolving around a star known as OGLE-2006-BLG-109L, which is about 1/2 the size of our sun and about 5,000 light years away.

“Microlensing technique works by making use of the gravity of the star as well as the Planet to bend and focus light rays from a Star in the background“, – said Scott Gaudi of Ohio State University. “If you are looking at a Star, and another goes by in the foreground will focus and bend light rays. This causes the magnification of the Star in the background.” – He added.

“Any planet revolving around the Star causes “a little bump” in the magnification effect,” Gaudi said.

The two planets in the new solar system are smaller than Saturn and Jupiter. The larger planet is slightly smaller than the Jupiter, with close to 70 percent of Jupiter’s mass. The smaller planet is about 30 percent of the mass of Jupiter, which makes it similar in size with Saturn.

Moreover, the two Planets are much nearer to their parent Star. The bigger planet is 2.3 astronomical units (AU) from its parent Star where as the smaller one is about 4.6 AUs from its Sun. In contrast to this in our solar system the Jupiter lies about 5.2 AUs from the sun while the Saturn is at a 9.5 Astronomical Units away from our sun.

The Sun i.e. the parent Star of the new solar system is dimmer than that of ours. However the temperatures in the two planets are similar to that of Jupiter and Saturn. This is because the planets are closer to their star than Jupiter and Saturn to our Sun.

The two planets are only the 5th and 6th identified using gravitational microlensing. “This is the first time a planet with Jupiter’s mass was identified where we had notable sensitivity to more planets. We may be able to find a full census of planetary systems in all over our galaxy,” – said Scott Gaudi.

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An artist’s imagination of hydrocarbon pools, icy and rocky terrain on the surface of Saturn’s largest moon Titan.
Credits: Steven Hobbs

The immense reserve is detected at a location which is 1.2 billion kilometers i.e., approximately 750 million miles away from Earth, where average temperature itself will be minus 179 degrees Celsius.

Titan has several hundreds times more liquid hydrocarbons than all the available oil and natural gas reserves on Earth, said the European Space Agency (ESA).

In Titan, the ethane and methane falls from the sky in the form of rain, forming massive lakes and seas. It is believed that complex organic molecules called tholins are responsible for Titan’s oily dunes, said the ESA.

“Titan is just enclosed in a carbon covered material. It is a giant factory of organic chemicals,” said scientist Ralph Lorenz.

Revealing the mystery of Titan’s carbon-chemistry may help to find out the answer for how Earth’s carbon-based life began, said the researchers.

The fall of hydrocarbons from the sky, in the form of rain and get stored in massive deposits that form lakes and dunes. But now scientists are quantifying the material using observations from NASA’s Cassini spacecraft.

Titan has long been considered as a place that might be somewhat like Earth. “The inventory of immense oil resource is an important break through into the geology and climate history of Titan.” said scientist Ralph Lorenz.

The 20 percent of Titan’s surface has been mapped by Cassini with the help of its radar. According to the statement of NASA, scientists have observed several hundreds of lakes and seas; each of it is estimated to have more hydrocarbon than all the known oil and natural gas reserves on Earth.

The total availability of natural gas on Earth is 130 billion tons. But the Titan’s lakes and seas individually have the equivalent of at least this much energy in the form of methane and ethane.

“This estimation is made based on the pictures of the lakes located in the North Polar Region,” Lorenz said. “We assumed that the southern polar region might also be similar, but we really don’t yet know how much liquid is there.”

The radar of Cassini has observed the southern polar region only once, and only two small lakes were identified.

Scientists also estimated the depth of Titan’s lakes by making some general assumptions based on the lakes on Earth.

“We know that the depth of some lakes are more than 10 meters or much deeper because they appear factually pitch-black to the radar,” said Ralph.

The volume of liquid present on the Titan’s surface is important because methane is a strong greenhouse gas. Titan will become much colder if the methane present on its surface gets expired. Scientists assume that the presence of methane in the Titan’s atmosphere might be due to the expulsion from volcanic eruptions.

Relevant Links: http://www.esa.int/esaSC/SEMCSUUHJCF_index_0.html

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