On the contrary, I think rampant speculation is a big part of the fun of anticipation, and in this case we get the satisfaction of knowing how wrong--er, right--we are in just a few short days!

Lots of people are seeing Titan; maybe familiarity from Cassini? It's totally Triton-like to me. Frost-covered plains and some tectonics.

Excellent summary of "the story so far" at Ceres. The bright spots are the clear winners of the popularity contest, though.

The problem with that comparison is that Johun is decidedly oblong, so that the "central ridge" is still indeed central with respect to the crater walls. The images of the bright-spot crater show it to be much more circular; while the brighter of the two spots is central, the dimmer is decidedly closer to the wall. Not saying it couldn't be an offshoot of the main bright spot, but it doesn't appear to be the endpoint of a "central ridge".

We'll see soon.

Good spot! And I'd call it valley-like, though not graben-like. There's definitely a broad low depression there.

I do get the impression there's less geology going on here than even Vesta, but still plenty to study.

Also, did anyone notice that the huge flat crater has a small sharp crater almost bullseyed in the middle, like in Caloris, only proportionally bigger? It's an odd coincidence, but cool-looking!

I hope it doesn't come across as patronizing to point out that what we have thought should be true has, so many times in this golden age of planetary exploration, been completely invalidated by what is actually out there. Little Miranda, for instance, has no business being anything other than a cratered lump, yet there those amazing coronae are. In a few weeks we'll doubtless have a clearer idea of what to argue about, but in the meantime I'm just going to enjoy the front-row seats to unfolding history.

You have to poke around a bit at the Gazetteer for Planetary Nomenclature, but it's there. Scroll down past the major planets to get to the asteroids. For Ceres, craters are global agriculture and vegetation deities, and other features are agriculture festivals.

The excellent rocker image gives a strong impression of a continuous chasm, but outside of that I get the impression of preserved crater walls down to and past the limit of resolution. As long as we're doing moon analogies, mine would be Mimas with the dense cratering.

Strange to think... Pluto has been known all my life, and yet, even this year, still many AU out, New Horizons will have the best-paced instruments ever to have studied it, and will massively add to our sum of knowledge even before encounter. Can't wait. Thanks for the news Alan!

Thanks for this useful heads-up.

LOOOOVE the Bradbury Landing icon!

What a job. John, you're kinda my hero.

The linked article mentions five instruments; the ISIS investigation uses two instruments, EPI-hi and EPI-lo, presumably to measure particles at different energies. It also discusses five investigations that have been funded, the fifth one being a project scientist that won't fly with the spacecraft. Obviously.

Another halfway point today:

Halfway Heliocentric Distance Traveled from Earth at Launch to Pluto at Flyby

June 14, 2010

16.946 AU

(from Dr. Alan.)

IMHO the "real" halfway point is the time one (days from launch to encounter) and that's in October. Tick, tick, tick....

When I read that article on the bus I so wanted to turn to the strangers next me and brag, "I posted to that thread!!!!" But I'm sure I was a lot more excited than they would be.

Alan, thanks for the info, but I'm a little confused... I assume that for crude shape information, you mean cut the maximum distance to 10⁶ kilometers, since 10⁶ diameters would be 10⁸ kilometers. But which do you mean for the "geology" figure? 30,000 diameters would be 3 million kilometers for our theoretical 100 km object, which is tough enough, but 30,000 kilometers is more or less a bullseye: better targeting than even Apophis will manage . It seems to me you could get at least some worthwhile surface-feature resolution at a greater distance than that. The famous LORRI images of Tvashtar's plume resolved fine details at 2.5 million km. On the other hand, I know that spacecraft (and ground) resources are limited, and you have to be sure you're getting enough meaningful data for any expenditure. Could you give any hints as to when you think it might be worthwhile to observe during one of these flybys?

I haven't finished the article yet, but from the abstract it seems like Kipping & Bakos have done a lot of the interesting and important follow-up of the data. Of particular interest is their constraints on resonant perturbers, exomoons and exotrojans... negative results are less sexy but provide interesting information as well.

As for Kepler's new data-withholding policy, I agree with Greg that it is understandable but may be wrongheaded, and it is interesting that ESA is moving in the opposite direction for PLATO, as ESA's specialist for both PLATO and COROT, Malcolm Fridlund, points out in the Nature article. "'You get a larger community and you get a bigger workforce for free,' he says. 'It's clear that the more people you get involved, the more support you get.'" Something for NASA to bear in mind when deciding whether to withhold KEPLER data, perhaps.

Those plume shots are spectacular. The level of fine detail is much higher than what I recall from previous Enceladus encounters. Can someone with more knowledge than me comment on this? Is it a consequence of higher resolution? A better viewing angle? Better tracking? Or has the Cassini crew just learned from past encounters how to optimize exposures for the plumes?

By "transit timing variation," are you referring to delays or advances in the transit time due to the planet's motion around a planet-moon barycenter? This is the method described in the discussion earlier in the thread. It would seem to me that, in order for such a system to be detectable with Kepler, the moon would need to be more massive, relative to the planet. We've found larger planets than Jupiter; it's only reasonable to assume that larger moons than Ganymede also exist. And such larger moons--if they indeed exist--could be detectable by their own transits across the star as well, I should think, especially if their presence was already suspected from the timing data.

Helvick's concern about the stability of moon orbits for hot Jupiters due to tides is notable, but again, if we tweak our hypothetical we might avoid it. Wouldn't there be more available stable orbits for a large moon of a planet in a 24-day orbit than of one in a 3-day orbit? As a bonus, the 24-day planet will have lower orbital speed and thus a longer transit, giving a longer sample of planet-moon interaction.

I haven't heard anyone talk about work on direct detection of moons transiting their planets. Any graduate students looking for a thesis idea?

One other possible source of noise occurs to me; it's also an opportunity for stellar studies, I suppose. If a planet crosses a large starspot, the variation in total light will be similar to its eclipsing a large moon. There are of course differences; the region surrounding a starspot is usually brighter than the average star surface, no? Has such an event been modeled? What would the resulting light curve look like?

I think "resolultion" in this case refers to time. According to the mission website, Kepler samples a star's brightness every fifteen minutes. I don't know how long a typical Kepler transit will be but in the preliminary list of COROT candidates the transits ranged from an hour up to sixteen hours, with perhaps three hours being the norm. So if we assume a transit takes three hours, we have only about a dozen samples per transit. That is a pretty small sample size from which to try and weed out moon data, and it is a reasonable question whether it will be possible. It seems to me that, if we have a particularly long, slow transit (say 8 hours), an unusually large moon (approaching Earth sized or at least larger than Mars), and a bit of luck, it will be possible, but won't be obvious in the raw data. However, over time Kepler will obviously accumulate observations of multiple transits for each planet detected by Kepler, so that with rigorous analysis it might be possible even with less extreme examples. This is more believable after seeing how clean and noise-free the data were at the Aug. 6 news conference.

As for a ring: Doug, I hadn't thought of it, but it will obviously wreak havoc with density assumptions at first, as first contact of the rings will be difficult to differentiate from the planet itself, giving a grossly inflated diameter estimate. I imagine the difference will become apparent over time, as more samples are added to the data set, but in the meantime someone will publish a paper they'll have to retract.

Yes, Steve, that's what I mean. I suppose it depends on what you mean by "signal," but the indication of the presence of a moon would be the magnitude difference between the star transited by both planet and moon and the the star transited only by the planet, because the moon is transiting the planet or being occulted by it. In my quick-and-dirty illustration (not to scale), on the left the star is transited by both star and moon, but on the right, the moon has moved in front of the planet as it tranits, resulting in slightly less occultation of the star. Is that clearer?

Thanks for the link back to moons... saved me the trouble of searching. There's something that's I've been thinking about regarding moon detection with Kepler data.

Most investigators seem to be focusing on the transit-timing method for detecting moons: the slight advance or delay of transit ingress and egress due to motion of the planet around the planet-moon barycenter. This timing variance will be slight, but within the edge of detectability. I also saw one reference to the possibility of slight additional dimming before or after the main transit due to the physical body of a large moon. For this to be possible, the moon will have to be very large indeed, approaching Earth diameter: much larger than Ganymede, but within the realm of conceivability.

For a moon this size, a possible third method of detection occurs to me. The Hill spheres of hot Jupiters are very small, so that even a moon in a high-inclination orbit is likely to transit and be occulted by its planet as seen from Earth (or Kepler). Also, it is likely to have a very short period even relative to the abbreviated "year" of the hot Jupiter, probably on the scale of hours. Won't we therefore see a signal as the moon passes in front of and behind the planet during transits? This signal will be much fainter than the main transit signal, of course, but shouldn't it be possible to tease it out? Over the course of time, as the number of observed planet-star transits increases, the observed moon-planet transits will increase at some multiple, enabling characterization of both the moon and the planet. Especially coupled with the barycenter/timing method mentioned above, this could tightly constrain masses and hence densities of exoplanets. Assuming, of course, that such moons exist.

I'm sure someone must be working on this; has anyone more familiar with the literature or the community seen or heard a mention?

Sorry to wander off-topic, but....

"Jovian" is from Jovis, the Latin genitive form of Jupiter, not the Greek name (which would of course be Ζεύς or Zeus). The same is true for Venerian (not venereal... tsk, tsk) and Martian. The forms Mercurian, Saturnian, Uranian and Neptunian work just fine, being formed in more or less the same way. Besides, Cronian means of the Klingon homeworld (ducks and runs for cover).

Anyway, as for maps: I still have my collection of hard-copy maps of the planets and moons from the eighties that I got as a kid and will keep forever. I regard them as historic, the first maps of these worlds, but yes, they are out-of-date. I did recently stumble across the USGS' current listing of I- maps (geologic investigation maps, the category under which they published the Voyager-based maps), but if you look under planetary maps you'll note that they stop at Jupiter. (They have nice new maps of all the Galileans except Io, available as PDFs.) However, the only Saturn maps I've found are the rough photomosaics available on the CICLOPS page; most don't even have nomenclature attached. I suppose you could put it there yourself and make a decent map, but I'm hoping at some point the USGS makes nice new maps of the Saturnian satellites (and also Mercury). Back in the Voyager era I was, as mentioned, just a kid, so I called the USGS in Flagstaff and asked them; I think I got put on the phone with the late Hal Mazursky. IIRC he told me it would be about 18 months after they got all the data from the Voyager encounters. So if the USGS even plans on publishing new Saturn maps, I'll bet they'll wait until "all" the data are in, and who knows when they'll judge that to be. Any opinions?

In the meantime, there are also PDFs available at the USGS' Gazetter of Planetary Nomenclature. And Google gave me this map of Mimas, though it's not listed. Hope this helps.

Clearly he was referring to the Hawaiian word meaning "to spread out". PhilCo knows some obscure Hawaiian.

Long time, first time.

I hope I'm not to late to be useful, but I noticed that following Nix backward in time from the date of the encounter, it drew closer and closer to Hydra. Following that all the way back to June 18, 2015 led to a close encounter, and at about 13:40 we get an interesting syzygy of all four bodies:

link

Not overly spectacular, but it does have the advantage of being nearly a month before the encounter and so hopefully during a, er, less busy time.

Actually, I really just wanted the opportunity to use the word syzygy.