Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Cassini-Huygens Looks At Phoebe’s Distant Past

15.06.2004


Images collected during the Cassini-Huygens close fly-by of Saturn’s moon Phoebe give strong evidence that the tiny moon may be rich of ice and covered by a thin layer of darker material.


Shown here is a mosaic of seven of the sharpest, highest resolution images taken of Phoebe during the Cassini-Huygens close fly-by of the tiny moon. The image scales range from 27 to 13 metres per pixel. Smaller and smaller craters can be detected as resolution increases from left to right. The number of blocks, or bumps on the surface also increases to the right. The Sun is coming from the right, so the bright-dark pattern is reversed between blocks and small craters. Grooves or chains of pits are seen on the left portion of the mosaic, which may mark fractures or faults induced by large impact events. Many of the small craters have bright rays, similar to recent craters on the Moon. There are also bright streaks on steep slopes, perhaps where loose material slid downhill during the seismic shaking of impact events. There are also places where especially dark materials are present, perhaps rich in carbon compounds.
Credits: NASA/ESA/ASI



Its surface is heavily battered, with large and small craters. It might be an ancient remnant of the formation of the Solar System.
On Friday 11 June, at 21:56 CET, the Cassini-Huygens spacecraft flew by Saturn’s outermost moon Phoebe, coming within approximately 2070 kilometres of the satellite’s surface. All eleven on-board instruments scheduled to be active at that time worked flawlessly and acquired data.

The first high-resolution images show a scarred surface, covered with craters of all sizes and large variation of brightness across the surface.



Phoebe is a peculiar moon amongst the 31 known satellites orbiting Saturn. Most of Saturn’s moons are bright but Phoebe is very dark and reflects only 6% of the Sun’s light. Another difference is that Phoebe revolves around the planet on a rather elongated orbit and in a direction opposite to that of the other large moons (a motion known as ’retrograde’ orbit).

All these hints suggested that Phoebe, rather than forming together with Saturn, was captured at a later stage. Scientists, however, do not know whether Phoebe was originally an asteroid or an object coming from the ’Kuiper Belt’.

The stunning images obtained by Cassini’s high-resolution camera now seem to indicate that it contains ice-rich material and is covered by a thin layer of dark material, probably 300-500 metres thick.

Scientists base this hypothesis on the observation of bright streaks in the rims of the largest craters, bright rays radiating from smaller craters, grooves running continuously across the surface of the moon and, most importantly, the presence of layers of dark material at the top of crater walls.

"The imaging team is in hot debate at the moment on the interpretations of our findings," said Dr Carolyn Porco, Cassini imaging team leader at the Space Science Institute in Boulder, USA.

"Based on our images, some of us are leaning towards the view that has been promoted recently, that Phoebe is probably ice-rich and may be an object originating in the outer solar system, more related to comets and Kuiper Belt objects than to asteroids."

The high-resolution images of Phoebe show a world of dramatic landforms, with landslides and linear structures such as grooves, ridges and chains of pits. Craters are ubiquitous, with many smaller than one kilometre.

"This means, besides the big ones, lots of projectiles smaller than 100 metres must have hit Phoebe," said Prof. Gerhard Neukum, Freie Universitaet Berlin, Germany, and a member of the imaging team. Whether these projectiles came from outside or within the Saturn system is debatable.

There is a suspicion that Phoebe, the largest of Saturn’s outer moons, might be parent to the other, much smaller retrograde outer moons that orbit Saturn. They could have resulted from the impact ejecta that formed the many craters on Phoebe.

Besides these stunning images, the instruments on board Cassini collected a wealth of other data, which will allow scientists to study the surface structures, determine the mass and composition of Phoebe and create a global map of it.

"If these additional data confirm that Phoebe is mostly ice, covered by layers of dust, this could mean that we are looking at a ’leftover’ from the formation of the Solar System about 4600 million years ago," said Dr Jean-Pierre Lebreton, ESA Huygens Project Scientist.

Phoebe might indeed be an icy wanderer from the distant outer reaches of the Solar System, which, like a comet, was dislodged from the Kuiper Belt and captured by Saturn when the planet was forming.

Whilst studying the nature of Phoebe may give scientists clues on the origin of the building blocks of the Solar System, more data are needed to reconstruct the history of our own neighbourhood in space.

With that aim, ESA’s Rosetta mission is on its way to study one of these primitive objects, Comet 67P/Churyumov-Gerasimenko, from close quarters for over a year and land a probe on it.

The fly-by of Phoebe on 11 June was the only one that Cassini-Huygens will perform with this mysterious moon. The mission will now take the spacecraft to its closest approach to Saturn on 1 July, when it will enter into orbit around the planet.

From there, it will conduct 76 orbits of Saturn over four years and execute 52 close encounters with seven other Saturnian moons. Of these, 45 will be with the largest and most interesting one, Titan. On 25 December, Cassini will release the Huygens probe, which will descend through Titan’s thick atmosphere to investigate its composition and complex organic chemistry.

Roberto Lo Verde | European Space Agency
Further information:
http://www.esa.int/SPECIALS/Cassini-Huygens/SEMNL63VQUD_0.html

More articles from Physics and Astronomy:

nachricht MSU astronomers discovered supermassive black hole in an ultracompact dwarf galaxy
14.08.2018 | Lomonosov Moscow State University

nachricht ASU astrophysicist helps discover that ultrahot planets have starlike atmospheres
13.08.2018 | Arizona State University

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: New interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

Im Focus: The “TRiC” to folding actin

Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.

Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...

Im Focus: Lining up surprising behaviors of superconductor with one of the world's strongest magnets

Scientists have discovered that the electrical resistance of a copper-oxide compound depends on the magnetic field in a very unusual way -- a finding that could help direct the search for materials that can perfectly conduct electricity at room temperatur

What happens when really powerful magnets--capable of producing magnetic fields nearly two million times stronger than Earth's--are applied to materials that...

Im Focus: World record: Fastest 3-D tomographic images at BESSY II

The quality of materials often depends on the manufacturing process. In casting and welding, for example, the rate at which melts solidify and the resulting microstructure of the alloy is important. With metallic foams as well, it depends on exactly how the foaming process takes place. To understand these processes fully requires fast sensing capability. The fastest 3D tomographic images to date have now been achieved at the BESSY II X-ray source operated by the Helmholtz-Zentrum Berlin.

Dr. Francisco Garcia-Moreno and his team have designed a turntable that rotates ultra-stably about its axis at a constant rotational speed. This really depends...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

2018 Work Research Conference

25.07.2018 | Event News

 
Latest News

'Building up' stretchable electronics to be as multipurpose as your smartphone

14.08.2018 | Information Technology

During HIV infection, antibody can block B cells from fighting pathogens

14.08.2018 | Life Sciences

First study on physical properties of giant cancer cells may inform new treatments

14.08.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>