When the last Voyager pictures from Neptune (and perhaps even more eagerly awaited, the images of Triton) came in back in 1989, I distinctly recall the sense of letdown that set in the following week. All those spectacular Voyager findings were, I then assumed, a thing of the past. But as we’ve seen, the Voyagers are robust little spacecraft, pushing on toward the heliospause and the edge of interstellar space. Still functional, one or both may be sending us signals when they make this final transition within the next ten to twenty years.
Which is not to say we don’t need follow-up missions to explore this territory (Innovative Interstellar Explorer, using radioisotope methods to power an ion engine, immediately comes to mind), but what a grand story the Voyagers continue to write. And consider this finding: Because the two spacecraft took entirely different routes, Voyager 2 is crossing the termination shock region some 20 billion kilometers away from Voyager 1’s present location. Voyager 2 is also almost two billion kilometers closer to the Sun. The upshot: The bubble created around our Solar System by the solar wind is clearly asymmetric.
Voyager’s most recent discovery will be discussed at the fall meeting of the American Geophysical Union at the Moscone Center in San Francisco from December 10 to 14. Other topics of interest to deep space advocates that help us take the pulse of current research and potential future missions:
- Cassini scientists Larry Esposito and Miodrag Sremcevic report on mounting support for the idea that Saturn’s rings are permanent rather than temporary features. The Cassini orbiter, yet another heroic spacecraft, is sending data showing that when ring particles fragment, they tend to re-group, keeping the overall ring structure more or less intact. If the work bears out, there goes the older idea that the rings are as recent as the dinosaurs.
- Members of the New Horizons team (including Johns Hopkins’ Ralph McNutt, a guiding force behind Innovative Interstellar Explorer) will talk about what the Pluto-bound New Horizons found as it barreled down the tail of Jupiter’s magnetosphere. Ponder this: Io alone ejects a ton per second of volcanic gases. These become ionized and accelerated by Jupiter’s magnetic field, a phenomenon New Horizons has now measured for a solid three months.
- I’m also glad to see William McKinnon (Washington University, St. Louis) reporting on the current view of Europa and its possible habitability under the ice. That session will feature three presentations, covering the possibility of radar sounding to search for water and a report on plans to deploy an autonomous underwater robotic vehicle in the Antarctic. Such a vehicle may become a prototype for future exploration on the Jovian moon.
Centauri Dreams, of course, focuses on the outer Solar System and the possibility of missions far beyond it, to the Kuiper Belt, the Oort Cloud, and one day the nearest stars. But while we’re talking about doughty spacecraft, let’s not forget the two that are much closer to home. The remarkable Spirit and Opportunity are now four years into Mars missions originally designed to last three months. In an era of continuing budget uncertainty, we are at least getting the most out of our spacecraft!
“Permanent” as in they’ll always be there…or is that a slippery term like “recent” when talking about geology!
Are we sure that there are “volcanos” on Io. Is it possible that Io is being etched (electro machined) by the plasma currents around Jupiter?
Regarding Europa, what would be really good (though probably not likely to happen unless space research ends up with a much bigger budget than it has now) would be to have a network of seismometers set up across its surface. Presumably the tidal stresses on the ice crust cause numerous “Europaquakes”, which could potentially reveal an awful lot about the moon’s structure.
A network of seismometers on the ocean floor of Europa might be even more interesting, but that’s even less likely to happen…
Of course New Horizons is also heading out of the Solar System. It may not have an ideal instrument suite and we may all be in nursing homes before it reaches ‘the outer limits’, but with its RTG I cant imagine some science wont be forthcoming if funding allows.
I also assume its heading out in a different direction to the 2 Voyagers.
P
Hi occam’s comic
Come on! We can see the plumes. Not everything is plasma currents – in fact very little is. I can see you’re a fan of Wal Thornhill and his crowd, but sometimes Occam’s Razor cuts both ways, especially when the surface colourings look like sulphur, just like volcanoes belch.
One thing New Horizons does not have is anything
resembling the Pioneer Plaques and Voyager Records.
Instead it is carrying basically trinkets (a quarter, a
piece of SpaceShip One) because the mission team
did not deem such a project worth their time.
Deciphering the probe and who made it won’t be
made any easier for either any ETI or our
spacefaring descendants who may find it one day,
as a result. It will certainly say something about the
state of general human thought on our view of and
place in the wider galaxy in this era, though.
Phil, see this link for all the emigrants:
http://www.heavens-above.com/solar-escape.asp
At the moment it’s traveling somewhat southerly of Voyager 1, so not a particularly unique trajectory. I didn’t check how much its final trajectory will differ from what it is now.
Ab initio Equation of State data for hydrogen, helium, and water and the internal structure of Jupiter
Authors: N. Nettelmann, B. Holst, A. Kietzmann, M. French, R. Redmer, D. Blaschke
(Submitted on 6 Dec 2007)
Abstract: The equation of state of hydrogen, helium, and water effects interior structure models of giant planets significantly. We present a new equation of state data table, LM-REOS, generated by large scale quantum molecular dynamics simulations for hydrogen, helium, and water in the warm dense matter regime, i.e.for megabar pressures and temperatures of several thousand Kelvin, and by advanced chemical methods in the complementary regions. The influence of LM-REOS on the structure of Jupiter is investigated and compared with state-of-the-art results within a standard three-layer model consistent with astrophysical observations of Jupiter. Our new Jupiter models predict an important impact of mixing effects of helium in hydrogen with respect to an altered compressibility and immiscibility.
Comments: using emulateapj.sty, 13 pages, 11 figures, submitted to ApJ
Subjects: Astrophysics (astro-ph)
Cite as: arXiv:0712.1019v1 [astro-ph]
Submission history
From: Nadine Nettelmann [view email]
[v1] Thu, 6 Dec 2007 18:12:24 GMT (167kb)
http://arxiv.org/abs/0712.1019
Saturn’s Rings May be Old Timers
SAN FRANCISCO, Calif. – New observations by NASA’s Cassini spacecraft indicate the rings of Saturn, once thought to have formed during the age of the dinosaurs, instead may have been created roughly 4.5 billion years ago, when the solar system was still under construction.
Larry Esposito, principal investigator for Cassini’s Ultraviolet Imaging Spectrograph at the University of Colorado, Boulder, said data from NASA’s Voyager spacecraft in the 1970s, and later from NASA’s Hubble Space Telescope, led scientists to believe Saturn’s rings were relatively youthful and likely created by a comet that shattered a large moon, perhaps 100 million years ago.
But ring features seen by instruments on Cassini — which arrived at Saturn in 2004 — indicate the rings were not formed by a single cataclysmic event. The ages of the different rings appear to vary significantly, and the ring material is continually being recycled, Esposito said.
“The evidence is consistent with the picture that Saturn has had rings all through its history,” said Esposito of the University of Colorado’s Laboratory for Atmospheric and Space Physics. “We see extensive, rapid recycling of ring material, in which moons are continually shattered into ring particles, which then gather together and re-form moons.”
Esposito and colleague Miodrag Sremcevic, also with the University of Colorado, are presenting these findings today in a news briefing at the meeting of the American Geophysical Union in San Francisco.
“We have discovered that the rings probably were not created just yesterday in cosmic time, and in this scenario, it is not just luck that we are seeing planetary rings now,” said Esposito. “They probably were always around but continually changing, and they will be around for many billions of years.”
Scientists had previously believed rings as old as Saturn itself should be darker due to ongoing pollution by the “infall” of meteoric dust, leaving telltale spectral signatures, Esposito said. But the new Cassini observations indicate the churning mass of ice and rock within Saturn’s gigantic ring system is likely much larger than previously estimated. This helps explain why the rings overall appear relatively bright to ground-based telescopes and spacecraft.
“The more mass there is in the rings, the more raw material there is for recycling, which essentially spreads this cosmic pollution around,” he said. “If this pollution is being shared by a much larger volume of ring material, it becomes diluted and helps explain why the rings appear brighter and more pristine than we expected.”
Esposito, who discovered Saturn’s faint F ring in 1979 using data from NASA’s Pioneer 11 spacecraft, said a paper by him and his colleagues appearing in an upcoming issue of the journal Icarus supports the theory that Saturn’s ring material is being continually recycled. Observing the flickering of starlight passing through the rings in a process known as stellar occultation, the researchers discovered 13 objects in the F ring ranging in size from 27 meters to 10 kilometers (30 yards to six miles) across.
Since most of the objects were translucent — indicating at least some starlight was passing through them — the researchers concluded they probably are temporary clumps of icy boulders that are continually collecting and disbanding due to the competing processes of shattering and coming together again. The team tagged the clumpy moonlets with cat names like “Mittens” and “Fluffy” because they appear to come and go unexpectedly over time and have multiple lives, said Esposito.
Esposito stressed that Saturn’s rings of the future won’t be the same rings we see today, likening them to great cities around the world like San Francisco, Berlin or Beijing. “While the cities themselves will go on for centuries or millennia, the faces of people on the streets will always be changing due to continual birth and aging of new citizens.”
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate in Washington, D.C.
For more information about the Cassini-Huygens mission, visit:
http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini .
To listen to a podcast of Esposito and view a short video animation of objects in Saturn’s F ring shattering and re-forming, visit:
http://www.colorado.edu/news/reports/space/ .
Return To Europa: A Closer Look Is Possible
December 13, 2007
Jupiter’s moon Europa is just as far away as ever, but new research is bringing scientists closer to being able to explore its tantalizing ice-covered ocean and determine its potential for harboring life.
“We’ve learned a lot about Europa in the past few years,” says William McKinnon, professor of Earth and Planetary Sciences at Washington University in St. Louis, Mo.
“Before we were almost sure that there was an ocean, but now the scientific community has come to a consensus that there most certainly is an ocean. We’re ready to take the next step and explore that ocean and the ice shell that overlays it. We have a number of new discoveries and techniques that can help us do that.”
McKinnon is discussing some of these recent findings and new opportunities for exploring Europa in a news briefing today at the meeting of the American Geophysical Union in San Francisco. He is joined by colleagues Donald Blankenship, research scientist at the Institute for Geophysics at the University of Texas at Austin’s Jackson School of Geosciences, and Peter Doran, associate professor of Earth and Environmental Sciences, University of Illinois at Chicago.
Full article here:
http://www.jsg.utexas.edu/news/rels/121307.html
Voyager’s Odyssey (pdf)
The two Voyager spacecraft transformed our view of Earth’s place
in the solar system, and 30 years after launch, they’re still going
where no one has gone before. More…
http://pr.caltech.edu/periodicals/EandS/articles/LXX4/voyagerlayout-web.pdf
From Rockets to Spacecraft: Making JPL a Place for Planetary
Science (pdf)
From its humble beginnings as a remote patch of the Arroyo Seco
used to test rockets, JPL has grown into the leading U.S. center for
robotic space exploration. More…
http://pr.caltech.edu/periodicals/EandS/articles/LXX4/explorerlayout-web.pdf
Despina, Moon of Neptune
Credit: NASA, JPL, Ted Stryk
Explanation: Despina is a tiny moon of Neptune. A mere 148 kilometers across, diminutive Despina was discovered in 1989, in images from the Voyager 2 spacecraft taken during its encounter with the solar system’s most distant gas giant planet.
But looking through the Voyager 2 data 20 years later, amateur image processor (and philosophy professor) Ted Stryk discovered something no one had recognized before — images that show the shadow of Despina in transit across Neptune’s blue cloud tops.
His composite view of Despina and its shadow is composed of four archival frames taken on August 24, 1989, separated by nine minutes. Despina itself has been artificially brightened to make it easier to see. In ancient Greek mythology, Despina is a daughter of Poseidon (the Roman god Neptune).
http://antwrp.gsfc.nasa.gov/apod/ap090903.html