NASA Spacecraft Spots New "Moonlet" In Saturn's Rings

wired.com:

NASA's Cassini spacecraft has discovered a new object in Saturn's rings.

By capitalizing on the angle of sunlight cast on the rings as the planet nears its August 11 equinox, Cassini captured the 25-mile long shadow cast on Saturn's B ring by a tiny moonlet that is probably around 1,300 feet in diameter.

Read the whole story: wired.com

Comments

[Dolphinfan65]

04:59 PM on 08/09/2009

WOW , science, never seems to amaze me any more, except for things like this.

[Soundofthunder]

02:01 PM on 08/09/2009

I thought a moonlet was when Verne Troyer drops his pants.

SOT

[discouragerofhesitancy]

02:00 PM on 08/09/2009

Wow! Imagine, an entire solar system, complete with moonlets orbiting its larger planets. Top that, an entire universe, and all in just 6,000 years!

[talkingdog]

03:45 PM on 08/09/2009

God said; 'let there be light.'

[confuseddemocrat]

08:36 AM on 08/09/2009

Why a "moonlet" and not an asteroid?

[GearRatio]

09:55 AM on 08/09/2009

Small sized bodies in captive orbits around planets are generally referred to as moons, or, if very small, moonlets. The term "asteroid" is used to describe bodies in orbit around the sun, no more than 10 AU or so distance, and not in orbit about any of the major planets. (There are a few known cases of asteroids that orbit each other.)

Asteroids also have some characteristic features of their mineral composition that are not shared by all moons, but, these distinctions are not so clear cut....

[jsarets]

04:30 AM on 08/09/2009

Cassini, like other outer solar system probes, is powered by plutonium-fueled radioisotope thermoelectric generators. People need to get over their irrational fear of nuclear power if mankind is ever to maintain an active presence throughout the solar system.

Fuel cells don't have the energy density and solar cells don't have the power density (or physical durability). Nuclear power is a nearly-essential technology for manned missions to Mars, and nuclear propulsion is a major enhancement. Compared to chemical and solar propulsion, nuclear propulsion extends the surface mission from 20 days to 2.5 years with the same mass to low earth orbit while substantially reducing transit times.

However, America hasn't launched a fission reactor into space since SNAP-10A in 1965. And while nuclear thermal rocket engines have been successfully ground-tested, they've never been flown. To be clear, I'm not advocating nuclear-powered launch vehicles. These would be upper stages whose reactors launched in a safe configuration and not activated until the spacecraft reaches a stable checkout orbit before departure for beyond-earth-orbit destinations.

Interplanetary spacecraft need robust radiation shielding anyway to protect from cosmic and solar radiation outside Earth's magnetosphere. A small shadow shield is the only added shielding required for a manned spacecraft with a nuclear powerplant.

[GearRatio]

07:35 AM on 08/09/2009

Read a bunch of technical papers, some years back, detailing design of the NERVA and Dumbo nuclear thermal rocket engines that NASA tested for space propulsion. Very impressive exhaust velocities, but, did spot what appeared to be a serious constraint on their usefulness. Problem is, once such an engine is fired, the high rates of fission in the reactor core during firing create enough radioactive daughter products that the core needs to be cooled thereafter to prevent it from melting.

This is not a problem before the engine in fired; pure plutonium, though radioactive, evolves a very modest amount of heat. Nor is it a problem when firing; the reactor's heat is carried away by the engine's exhaust. (That is, after all the point of the exercise!) But, once fired, the idled engine will require some hundreds of megawatts of cooling to keep it at a safe temperature. That sort of heat shedding capacity, in the insulating vacuum of space, will require quite large radiator panels, large enough, I suspect, to nullify the nuclear engine's performance advantage.

Perhaps a more optimum solution might be to equip the hypothetical Mars spacecraft with a modest sized (several hundred kilowatt) nuclear reactor, and use its electrical power output to drive a low thrust, high impulse, continuous duty engine. The VASIMIR ion engine comes to mind as a likely candidate. if it can be made to work reliably....

[jsarets]

03:13 PM on 08/09/2009

No, you just plan the burn so that the liquid hydrogen propellant/coolant keeps flowing over the core after the reactor shuts down, providing a predictable amount of residual impulse at the end of the burn while the reactor cools down.

VASIMR requires huge sophisticated radiators. NTP doesn't if you do it right.

[PresidentRobertBooth]

01:55 AM on 08/09/2009

Saturn is breathtakingly beautiful and dazzling.


http://upload.wikimedia.org/wikipedia/commons/9/96/Saturn_eclipse_exaggerated.jpg

[ModernTimes1]

02:18 AM on 08/09/2009

Wonder how much of this pic is altered and/or enhanced. Regardless, it looks stunning.

[PresidentRobertBooth]

03:09 AM on 08/09/2009

The brightness has been enhanced.

That's all.

[bungle]

10:09 PM on 08/08/2009

fascinating. would love to see pics from inside the rings..

[GearRatio]

10:56 PM on 08/08/2009

Heh! Suspect that the rings are cluttered enough with debris, from dust to gravel to boulders, that a spacecraft taking pictures from inside rings would have a short life....

[Motes]

09:50 PM on 08/08/2009

Given the three previous comments I guess it answers why most science articles are relegated to the back-end of the green section. There really is not any interest in people trying to understand how the universe works given the clues we are given from our various spacecraft. You know just one set of questions that science is looking at and which people could be talking about.
How stable an orbit would the moonlet need in order for to remain so close to the ring? Could it enter the ring frequently without its orbit destabilizing or it agglomerating more mass from impacts from the ring? I guess if we were interested we would be blogging about that as opposed to a bunch of lameass jokes

[SamEllison]

10:42 PM on 08/08/2009

I would guess it is in a stable orbit and probably part of the ring.
The ring can not be seen with a camera, only 30' thick, without
the Sun illuminating the shadow.

Doesn't that ring resemble a bar-code?
Life imitates nature!

[GearRatio]

10:53 PM on 08/08/2009

Well, if they can get at least one more photo, they can plot an orbit, see if it's stable or not. As well, an additional image would likely show a difference in the size of shadow cast on the ring proper, allowing some estimate of whether object's orbit is inclined relative to ring plane...

A bit surprised that an object as large as that hasn't created a minor gap; some of the "classical" ring gaps were found to be due to "shepherd" moonlets, IIRC.

Gotta say, though, have been quite beguiled by the "close up" images returned by Voyager and now Cassini, showing the astonishingly intricate structure of Saturn's rings. I mean, spokes, fer Goodness' sake! Who would have thought?

[stephanemot]

09:31 PM on 08/08/2009

This picture is a hoax. I recognised Wolfowitz's comb.

[ModernTimes1]

11:49 PM on 08/08/2009

It is amazing how many people being blissfully ignorant of a subject presume to post some utter nonsense instead.

[SonofLiberty1]

12:35 AM on 08/09/2009

Most of the folks here who post no next to nothing about astronomy.

[SonofLiberty1]

12:36 AM on 08/09/2009

Ha...no instead of Know:)

[LLNYRN]

09:02 PM on 08/08/2009

Could be one of those ships from "SILENT RUNNING".

Or a Monolith possibly?

[wadenelson1]

08:42 PM on 08/08/2009

Did they remember to clean the lens --- THIS TIME.