Saturday, February 26, 2005
- Titan's Sub-Saturnian H. While this clear filter image shows mostly atmospheric features, but some surface features, like the prominent "H", can be discerned.
- Large Crater on Hyperion. The image shows a large impact crater on Hyperion, ~100 km across [note: haven't quite measured this yet]. Could this be Bond-Lassell Dorsa? If a crater, would a 100 km wide crater on a world the size of Hyperion have a central peak?
- Saturn as viewed from Titan. Obviously this image was taken from Cassini, not from Titan. But this image does give an idea of what Saturn would look like from Titan's surface. Saturn would only be viewable from Titan within methane windows in the spectrum. Secondly, unlike all those idealic images of Saturn from Titan showing the majestic rings, Saturn's rings would be edge-on and would not be seen but for a narrow line.
Friday, February 25, 2005
Thursday, February 24, 2005
- Phoebe has a mean radius of 106.6 ± 1 km and a density of 1.630 ± .045 g/cm3
- Layering on Phoebe suggests an oversaturation of impact events as more recent impacts excavate older impact ejecta
- Iapetus has three large impact basins within Cassini Regio, each with at least suggested central rises.
- Crater counts performed within the southern portion of the trailing hemisphere confirm the old age of Iapetus' surface as suggested by Voyager.
- Impact features within the equatorial ridge suggest that it is not the youngest feature on the surface. The lack of bright crater floors within Cassini Regio suggests that the leading hemisphere darkening is a fairly young feature.
- With regards to the bright/dark albedo asymmetry, Bright southern crater rims, dark northern crater rims, and dark north-trending streams in the bright-dark transition region suggest "long-distance, ballistic" transport of the dark material. This could be due to exogenic or endogenic causes, but the authors tend toward exogenic since a reasonable heat source needed for endogenic venting could not be found.
While not completely outer satellite related, CICLOPS has released other images related to this week's Science Cassini Special Issue. The best of the bunch is this view of Saturn, a mosaic consisting 42 frames (each consisting of three merged color images) showing the majesty that is Saturn. Other images released include a color view of the Dragon cloud, a storm system seen in the southern hemisphere of Saturn in mid-September of last year, as well as a series of images highlighting newly discovered ring features and evidence for an unseen moon in the Keeler Gap of the outer A ring.
Later today, we should see releases from other teams but I wouldn't count on it. When the papers show up on the Science magazine website, you can be sure that I will post the important satellite-related news here.
The European Southern Observatory in Chile has released some new images and spectra taken of Titan during the Huygens landing by the Very Large Telescope's adaptive optics NAOS/CONICA instrument. The images produces are some of the clearest views of Titan taken from Earth. They clearly show prominent features in the anti-Saturn hemisphere, like the bright dark boundary on the western side of Xanadu, the landing site region, and the "Eye of the Dragon". Their best images come from the 1.6 micron methane window (as opposed to the 2.0 micron window that the Keck group uses). The results presented today do bode well for performing regional spectroscopy on Titan in conjunction with VIMS on Cassini (which has a higher spatial resolution but a lower spectral resolution) though their lack of temporal resolution compared to the Keck group will make their results a bit weaker I think for tracking changes in Titan's atmosphere.
Results from last year were reported on the prior incarnation of this blog.
As part of a set of images related to the Science Cassini Special Issue, CICLOPS has released a pair of images showing a series of images of Phoebe taken last June. The images show feature names selected for various craters on the satellite. The names derive from the the Greek story of Jason and the Argonauts. The largest crater is Jason, named after the title character, or me, which ever you prefer.
This Enceladus image released last week is the Astronomy Picture of the Day.
CICLOPS has released a new low-resolution view of Telesto, the leading trojan of Tethys. The Saturnian system is unique for having sets of co-orbital satellites. Janus and Epimetheus swap orbits every few years. Other satellites revolve around the L4 and L5 Lagrange points of Dione and Tethys. Helene and Polydeuces are leading and trailing trojans of Dione, respectively. Telesto and Calypso are leading and trailing trojans of Tethys, respectively. The resolution on Telesto in this image is 7 km/pixel.
Wednesday, February 23, 2005
CICLOPS has released a newly processed frame showing a portion of western Xanadu. The pixel scale is 680 meters, but atmospheric scattering reduces the resolution to 5 times that value. A variety of albedo marking are seen in this image. What they are is still open to interpretation. The E-W short linear feature, for example, could be a volcanic fissure or tectonic. The lower portion of the image is part of a bright region in southwestern Xanadu that is the brightest area on Titan.
Higher resolution views of this area were released in December from Ta and Tb.
Update: Turns out that the moon in the background is not Tethys, but is instead Rhea. Also, MizarKey at the forum thread linked in this post's title has created an animated gif showing the mutual event.
Update2: Thanks to the Solar System Simulator for confirming the background moon as Rhea (compare with the Cassini view).
Titan Rising: Part I
Titan Rising: Part II
CICLOPS has released a new view of Mimas demonstrating the stability of the spacecraft pointing. The image shows Mimas against the backdrop of a ring-shadowed Saturn. For the observation, the spacecraft tracked Mimas during the exposure, leaving Mimas unsmeared while Saturn is smeared. The image was taken last month and the resolution on Mimas is 7 km/pixel.
Tuesday, February 22, 2005
CICLOPS has released a new image of Tethys taken last month that shows three prominent craters along the eastern limb of Tethys: Phemius, Polyphemus, and Ajax. A better view of these craters was taken in October. That image shows these craters running from top to bottom in the middle of the disk.
Gsnorgathon over at the MER Forum posted a message regarding a new program that shows a solar plot on Titan, as well as showing local panoramas (that show where the sun, Earth, and Saurn are in the sky at a particular point on Titan), as well as local time of a particular point on Titan. The program is quite customizable, allowing the user to add their own maps and add new locations to its database of Titan landmarks as features are named. Definitely a useful program.
Monday, February 21, 2005
Thanks to imran for the heads up.