Friday, March 04, 2005
Astronomy and Sky and Telescope Titan Special Issues
Update: Astronomy magazine's article not only has the official DISR created mosaics, but several mosaics created by Enthusiasts. Just thought that was interesting. Nothing significantly newsworthy, other than the figure that the probe swung less than 3 degrees in the troposphere. Sky and Telescope does have a few additional tidbits. First, according to GCMS team member Sushil Atreya said that GCMS detected 100% CH4 relative humidity at an altitude of 17-20 km, suggesting a thick cloud or haze layer at that altitude.
Thursday, March 03, 2005
As a followup to a report last Wednesday, CICLOPS has released a new movie showing a mutual event between Dione (in the foreground) and Rhea (800,000 km in the background). While Rhea is much larger than Dione, the distance between the two causes them to appear to have the same angular size. This also caused the initial confusion as to which moon was the background moon, first thought to be Tethys.
This is the first of two movies showing Saturn's moons released today. In this movie (one frame of which shown above), Mimas is seen along a small part of its orbit. Motion is made obvious by the changing aspect of the background rings. The non-circular nature of the limb is due to the large crater Herscel being on the limb in this view.
This newly released frame from CICLOPS shows Enceladus and Tethys in the same narrow angle frame. This image was taken in late January and is the first of many such compositions now that Cassini is orbiting in Saturn's equatorial plane and in the orbital plane of most of Saturn's major moons.
Wednesday, March 02, 2005
One very interesting discovery in this mosaic are two roughly east-west, dark parallel lineaments on the other side of the bright island/peninsula from the landing site. Obviously it is a bit difficult to determine the nature of these from these images, but certainly tectonics would be the first guess. The bright features within the dark terrain seem to focused mostly around the margin of the terrain, maybe former bright terrain that has been been eroded back to the current "shoreline".
- Odysseus crater is prominent in this shot of Tethys against Saturn's night side
- Interesting topography and albedo on Rhea north of Izanagi
- Two images of Iapetus' Cassini Regio here and here
- Dione's Padua Linea
Correction: That is not Saturn in the background. I was kinda thrown off by the full on anti-Saturnian hemisphere view of Tethys.
For those who can't stand edited transcripts, if you have RealPlayer, why not listen to the talk? Or for those who don't have the time to read the edited transcript and just want the nuts and bolts, read my summary.
Thanks to imran at the MER forum for the heads up.
Lack of Updates
Tuesday, March 01, 2005
- Sotin et al. describes geologic results from VIMS. They note a circular feature that may be an impact crater.
- Schwingenschuh et al. describes "fluctuations of the electric field up to 10 kHz" from the Permittivity, Wave, and Altimetry experiment on HASI found below 140 km.
- Teanby et al. describes work using CIRS to determin latitudinal variations in HCN in Titan's stratosphere. They find that abundances increase, indicative of downwelling in the north polar region.
- Iess et al. describes estimates for Iapetus' mass. Their density for Iapetus based on the two recent encounters is 1.106 cm/m3
- McCord et al. reports on composition variations on Titan using the VIMS instrument. Through the spectral windows available to them, McCord et al. has identified water ice as a surface component. In addition, they note differences in spectual properties at a very bright region centered around 26S, 118W (seen by ISS in the bottom half of this released image).
- Rannou et al. describes their circulation and how it tackles the problem of the strong extinction inversion layer in the troposphere. They suggest "that ethane and methane form clouds on aerosols and produce an extinction inversion layer by a strong rainout process".
CICLOPS has released this newly processed view of three of Saturn's small, inner satellites: (from right to left) Pandora, Janus, and Prometheus. Each of these moons are considered "ring moons" for their influence on the orbital paths of Saturnian ring particles. Janus, the large moon in the center of this image, nearly shares and in fact swaps orbits every four years with a slightly smaller moon named Epimetheus. The next swap is scheduled for February 2006. The moons Pandora and Prometheus act as "shepards" to the the thin F ring, keeping ring particles in the ring.
Monday, February 28, 2005
Sunday, February 27, 2005
A group of astronomers at the Keck Telescope on Hawaii's Big Island led by Antonin Bouchez captured this image of Titan using a filter sensitive to infrared light at around 2 microns, a relatively "clear" methane window. Keck images of Titan this year have generally shown a cloud-free atmosphere. Clouds during this time of Titan's year are generally focused in the southern polar latitudes between 70S and 90S and in the southern mid-latitudes near 40S. However, lately, fewer and fewer clouds have been seen. Only a couple of small south polar clouds were seen during the T3 flyby by Cassini. It is still unclear whether we are just getting unlucky lately in trying to look for clouds or whether Titan is in the middle of somekind of seasonal climate change as Titan approaches the August 3, 2009 vernal equinox.
On a sidenote, Cassini observed Titan in the clear filter at around this same time.
Update: I should have made it clear that this image was taken on February 25.
Hyperion's large crater (when compared to its size) continues to rotate into view in this new Cassini raw image.