In a few days, the phenomenal Saturn probe Cassini will skim just barely over the surface of the icy moon Enceladus. This is the moon that has gigantic plumes of water ice billowing out into space, the origin of which is still being argued.
The spacecraft will blow past the moon on March 12, at 19:06 UT. It’ll pass just 50 kilometers (30 miles) over the southern hemisphere of Enceladus. Unfortunately, it won’t take any images at closest approach — screaming over the landscape at 9 miles per second isn’t going to get you much more than blurry pictures. But it’ll take plenty of images on the way in and out, and while it does so its other instruments will be busily taking data, helping Earthbound scientists figure out just what the heck that tiny moon is doing.
Cassini will also pass right through the ice plume (generally considered an E-ticket ride) and will hopefully return an analysis of its contents.
You can read all about this in amazing detail on the CICLOPS site. There are timelines, maps, schedules, everything you could possibly need to understand this close encounter. Actually, you should take a look at that page if only to see what incredibly detailed thinking has to go into making such a pass. It’s amazing.
March 6th, 2008 at 11:17 am
All photos will be rated “R”?
J/P=?
March 6th, 2008 at 11:28 am
You can see a video description of the flyby on the JPL homepage at www.jpl.nasa.gov. See Enceladus: Taking the Plunge.
March 6th, 2008 at 11:29 am
So let me get this straight: Cassini and Enceladus are about one billion miles away (depending on orbital location) and it’s going to miss by all of 30 miles???? Yikes^3!
March 6th, 2008 at 11:40 am
I’m just wondering if Cassini could have become negatively charged. There could be firestorms and earthquakes on Enceladus as a result. Oh wait a minute, they already have plumes? See, it’s already affected it!!!
March 6th, 2008 at 12:59 pm
Pfft! Wake me up when Cassini can fly by close enough to leave a mark on the surface.
March 6th, 2008 at 2:01 pm
Is there no cause for concern that Cassini could be damaged by the ice plume?
March 6th, 2008 at 2:18 pm
Yea - what Ian said. What if the ice plume has rocks in it? Or is this moon ice covered too deeply for that?
March 6th, 2008 at 2:23 pm
At the risk of sounding stupid(er), would/will Cassini’s trajectory be affected by passing so close to Enceladus?
March 6th, 2008 at 3:04 pm
Peter:
Yes, absolutely. But the effect of gravity is precisely predictable, and it’s accounted for. Enceladus also has a trace atmosphere which will exert a small drag force, but I doubt it would be enough to cause any significant effect.
March 6th, 2008 at 3:15 pm
How thin are these plumes? I’m with Ian and Mike, hitting any degree of water a 9km/s cannot be a good thing even if you’re the size of a bus.
March 6th, 2008 at 3:17 pm
this is the plasma guys’ take on what is going on:
“The folks at NASA are baffled. They’ve known for several months that Saturn’s icy moon Enceladus emits unexpected jets. But now project scientists face a daunting task—to find the mysterious and highly improbable “source beneath the surface”.
Just a few days ago a NASA news release announced that the Cassini spacecraft exploring Saturn’s icy realm “may have found evidence of liquid water reservoirs that erupt in Yellowstone-like geysers on Saturn’s moon Enceladus”.
High-resolution Cassini images show icy jets and towering plumes ejecting huge quantities of ice particles at high speed. Project scientists are struggling to understand how this occurs.
The jets are found near the south pole of the 504 kilometer diameter moon, a region recently found to be significantly warmer than models had predicted. (In the image we’ve placed here NASA assigned faint light levels different colors to enhance visibility).
The finding flipped everything scientists knew about Enceladus on its head, because what should have been a dead moon appeared to be geologically active and what was supposed to be the moon’s coldest region turned out to be its warmest”, reports Space.com. (See our earlier Picture of the Day, “The Hot Poles of Enceladus”)
“This is as astonishing as if we’d flown past Earth and found that Antarctica was warmer than the Sahara,” said John Spencer, an astronomer from the Southwest Research Institute in Colorado and a co-investigator of the Cassini mission”.
In a classic understatement of the theoretical challenge, a NASA news release announced, “The rare occurrence of liquid water so near the surface raises many new questions about this mysterious moon”.
Water “so near the surface”? All we can see is ice on the surface—and icy plumes 480 kilometers high. But conditioned perception declares that liquid water must be present under the surface (like a Yellowstone geyser), in order for it to erupt in high-speed jets. The prior theoretical framework remains untouched even in the face of a stunning surprise.
Cassini’s imaging team leader Carolyn Porco seemed well aware of the potential discomfort from such a revelation. “We realize that this is a radical conclusion—that we may have evidence for liquid water within a body so small and so cold”, she said. “However, if we are right, we have significantly broadened the diversity of solar system environments where we might possibly have conditions suitable for living organisms”.
Or perhaps there is another possibility, one lying beyond the headline value of a possible environment “suitable for living organisms”. How about something more sweeping—a more accurate way of seeing the physical universe as a whole, our solar system included? How about a mind-altering discovery that could re-inspire all of science and scientific education?
The jets are signposts—part of a great collection of signposts pointing in one direction—to the inescapable but unacknowledged role of electricity in our solar system.
Despite the anomalous “warmth” of Enceladus’ south pole, it is a very cold place—minus 261 degrees Fahrenheit! But because it is warmer than it “should” be, NASA scientists jumped to the conclusion that liquid water beneath the surface must be responsible for both the temperature anomaly and the jets.
The only sources of energy available to planetary scientists are solar heating and internal heating (tidal and radioactive). Solar heating is completely inadequate, as all project scientists admit. And why would tidal heating be restricted to the southern hemisphere?
In their strain to explain the jets of Enceladus, the scientists face the same problem confronting theorists trying to explain cometary jets. And they have resorted to the same ad hoc invention of narrow surface vents above a subsurface chamber of (heated, liquid) water. There is no evidence of such vents, either on comets or on Enceladus. Nor have scientists, using their limited toolkit, ever found plausible ways of producing liquid water in the deep freeze of space
On Enceladus, the jets seem to originate from leveed channels, called “Tiger Stripes”, eerily similar to channels seen on Jupiter’s moon Europa. (We’ve placed an image of the “Tiger Stripes” here). These stripes are part of a vast and intricate complex of channels on Enceladus that match perfectly the behavior of electric arcs in simple laboratory experiments.
Electrical theorist Wallace Thornhill and his colleagues suggest there is no geyser of subsurface water analogous to the Yellowstone geyser. They say that if NASA will look they will find that the jets move across the surface. And in their motion across the surface, the electric arcs that produce the jets are creating the observed channels as they excavate material from the surface and accelerate it into space.
A strong parallel to the Enceladus plumes is provided by the so-called “volcanoes” of Jupiter’s moon Io. As NASA itself has confirmed, these bright plumes have moved many miles across the surface in the course of observation over a few decades, excavating material and accelerating it upward in jets that precisely match the predictions of a “plasma gun” model.
In the case of Enceladus, a Yellowstone type geyser requires a mixture of vapor, liquid, and ice particles – such a “cold” geyser would require pure water at a temperature of 273K (0? C) or above, less than 10 meters from the surface. For such a string of unlikely conditions, the probability rapidly approaches zero.
Testing the possibility that Enceladus’ jets are electrical—a virtual certainty in the eyes of the electric theorists—should be an immediate priority, before scientists convince themselves that we should embark on another expensive and misguided quest for life on a tiny frozen moon in the outer solar system.
Enceladus orbits in the inner regions of Saturn’s magnetosphere where the particle flux is high. But “particle flux” is typically nothing more than an astrophysical euphemism for an electrical current. And electric currents in space follow magnetic field lines. Within Saturn’s magnetosphere Enceladus will encounter currents in the polar regions. It seems probable that the south polar region of Enceladus has its own magnetic field, which could concentrate an electrical current in that region. In fact, sharp gradients in the magnetic field were encountered during Cassini’s closest approach to Enceladus—a typical indicator of current boundaries.
Planetary scientists continue to perpetuate misunderstanding when they call the “Tiger Stripes” of Enceladus “cracks” that allow water to reach the surface. The channels are, in fact, precise analogs of those seen on Europa. Their frequent parallelism, their ridges or levees, and their ability to cut across all other channels in their paths stand as a definitive contradiction of the “fracturing” hypothesis. The pictures suggest something akin to a “claw” or router bit dragged across the surface in disregard for prior surface relief. That is a unique signature of an electric arc. In contrast, fracturing is invariably affected by a pre-existing surface channel or groove, as anyone who has ever worked with a glasscutter knows very well.
The puzzle of the “Tiger Stripes” parallelism can be simply explained by the phase-locked rotation of Enceladus about Saturn (it keeps the same face toward the gas giant), working in combination with the symmetrical, axially aligned magnetic field of Saturn. This unique alignment will naturally cause the magnetic field lines and their associated discharge currents to move in parallel to each other near the pole of Enceladus as it orbits Saturn. (Further constraints on the pattern may be due to a remnant intrinsic magnetic field in the south polar region).
As for the anomalous temperature readings in the region of jet activity, Thornhill suggests that the readings are way below what project scientists will find if they will measure the temperature at the focal point of a surface jet. Electric discharges become focused and hottest where they touch down on a surface. We are reminded that it was Thornhill who alone predicted that the plumes of the icy moon Io would be much hotter than NASA had ever contemplated. When the Galileo probe took a close look, the radiation overloaded the camera. NASA had not prepared for the surprise. ”
Testable predections from the plasma guys, lets see how they do.
March 6th, 2008 at 3:53 pm
I would like to know, if all the activity in the solar system is produced by electric currents, why this doesn’t appear to be the case for Earth? Why is it that we do not see massive electric currents driving the volcanoes on this planet? Why isn’t the East African Rift Valley or the Mid-Atlantic Ridge a massive electrical arc discharge? Surely something of the Earth’s geology should be driven by some of these currents?
Perhaps Earth is unique in that it is not driven by massive electrical discharges. That kind of stuff only happens “up there” maybe.
Or perhaps the plasma guys are talking a load of rubbish.
March 6th, 2008 at 5:17 pm
Andy,
BA says that skepticism is something to be valued. You know, “I likes reality the way it is”
Here is a chance to be skeptical of both the Currently Accepted Version of Reality and Rubbish Filled Crank Version of Reality and put them both to the test.
The Plasma guys are saying “Enceladus’ jets are electrical—a virtual certainty” and they make a series of predictions based on their model.
1) The south polar region of Enceladus has its own magnetic field, which concentrates an electrical current in that region.
2) The jets of material move.
3) This movement causes the features called Tigers stripes
4) The materials being accelerated off the surface comes form a small very hot points at the leading edge of a growing Tiger Stripe.
And if you follow the logic of their model you might be able to come up with some more testable differences like: very small particle size for material in the jets, a charge on the material being jetted out, the hot points that are jetting the material should glow in the UV range.
Can someone else come up with some testable predictions based on a a tidally heated geyser model? It would be fun to compare them to data we get from the instruments.
And if the Plasma guys are wrong you can point to this as confirmation they are cranks not worth listening to!
March 6th, 2008 at 11:36 pm
The risk is addressed in the JPL video.
http://www.jpl.nasa.gov/videos/cassini/enceladus20080304/
March 7th, 2008 at 3:20 am
Quoth the BA :
“Cassini will also pass right through the ice plume (generally considered an E-ticket ride) ”
Um .. Que?
I’m afraid I don’t have a clue what that’s about. Could you - or anyone else - please explain what that bracketed bit means?
Cassini kissing Enceladus - Aawwww .. How romantic!
A frigid moon in the depths of space and an inanimate robot getting together .. How sweet! I just hope their relationship doesn’t get any closer or they might fuse together - & that’ll be that folks! ;-)..
March 7th, 2008 at 12:25 pm
While others have addressed Ian’s concerns about the dangers of Cassini passing through Enceladus’ plume, I just want to add that we don’t always make great discoveries without taking some risks. And with Cassini very close to the end of its primary mission, we should have met substantially all of the mission objectives by now, so the downside is comparatively low. The Cassini extended mission is icing on the cake, and while I would love to see an extended mission as productive as the Mars rover extended mission(s), we got what we came for and a whole lot more.
March 7th, 2008 at 8:25 pm
StevoR says: “Quoth the BA : ‘Cassini will also pass right through the ice plume (generally considered an E-ticket ride) ‘. I’m afraid I don’t have a clue what that’s about. Could you - or anyone else - please explain what that bracketed bit means?”
Short version:
When Disneyland opened in the mid ’50s, the admission was 25 cents (really!) but everything inside was extra. To go on the rides you bought a book of ride “coupons” (but everyone called them “tickets”). The coupons ranged from “A” for the simple rides (like the Main Street horse drawn trolley) to “D” for rides like the “Mark Twain” riverboat and “Rocket to the Moon” attractions.
When the park expanded to big rides, like the Submarines, Matterhorn Bobsleds and Monorail, in 1959, they added another level of coupon, the “E-Ticket”. This was the most coveted in the book. The term has been exported from Disneyland to the general vernacular in that the ultimate experience in any genre is referred to as “an ‘E Ticket’ ride”. Sally Ride helped the phrase along after reaching orbit on her first Shuttle mission by claiming it to be “A real ‘E-Ticket’.” The irony is that Disneyland had abandoned the coupon book idea by that time and gone to the single high-priced entry fee with the rides included.
For a more complete version, check out:
http://en.wikipedia.org/wiki/E_ticket
- Jack