Friday, October 31, 2014

Cassini see sunlight being reflected by the methane lakes

This near-infrared, colour mosaic from NASA’s Cassini spacecraft shows the sun glinting off of Titan’s north polar seas. While Cassini has captured, separately, views of the polar seas and the sun glinting off of them in the past, this is the first time both have been seen together in the same view.
The sunglint, also called a specular reflection, is the bright area near the 11 o’clock position at upper left. This mirror-like reflection, known as the specular point, is in the south of Titan’s largest sea, Kraken Mare, just north of an island archipelago separating two separate parts of the sea.

This particular sunglint was so bright as to saturate the detector of Cassini’s Visual and Infrared Mapping Spectrometer (VIMS) instrument, which captures the view. It is also the sunglint seen with the highest observation elevation so far — the sun was a full 40 degrees above the horizon as seen from Kraken Mare at this time — much higher than the 22 degrees seen earlier. Because it was so bright, this glint was visible through the haze at much lower wavelengths than before, down to 1.3 microns.

The southern portion of Kraken Mare (the area surrounding the specular feature toward upper left) displays a “bathtub ring” — a bright margin of evaporate deposits — which indicates that the sea was larger at some point in the past and has become smaller due to evaporation. The deposits are material left behind after the methane & ethane liquid evaporates, somewhat akin to the saline crust on a salt flat.

The highest resolution data from this flyby — the area seen immediately to the right of the sunglint — cover the labyrinth of channels that connect Kraken Mare to another large sea, Ligeia Mare. Ligeia Mare itself is partially covered in its northern reaches by a bright, arrow-shaped complex of clouds. The clouds are made of liquid methane droplets, and could be actively refilling the lakes with rainfall.

The view was acquired during Cassini’s August 21, 2014, flyby of Titan, also referred to as “T104″ by the Cassini team.

The view contains real colour information, although it is not the natural colour the human eye would see. Here, red in the image corresponds to 5.0 microns, green to 2.0 microns, and blue to 1.3 microns. These wavelengths correspond to atmospheric windows through which Titan’s surface is visible. The unaided human eye would see nothing but haze.

Friday, October 17, 2014

NASA Probe Zapped by Saturn Moon's Static

A spacecraft exploring the Saturn system was zapped by static electricity sent out by one of the ringed wonder's many moons in 2005, a new study suggests.
In fact, scientists have found that the Cassini spacecraft was "briefly bathed in a beam of electrons"
 coming from the moon Hyperion's surface, NASA officials said. No, this isn't proof of alien life: The particle beam was likely generated by the odd, porous moon's exposure to ultraviolet radiation from the sun and Saturn's magnetic field.
It was rather like Cassini receiving a 200-volt electric shock from Hyperion, even though they were over 2,000 kilometers [1,200 miles] apart at the time.
The study presents some surprising results. Scientists studying Saturn and its moons didn't think that the small, sponge-looking moon Hyperion could have any major interaction with the ringed planet's magnetosphere.
Researchers have long known that static electricity is an important phenomenon on Earth's moon. However, this is the first time they have confirmation of static at play on another cosmic body. Luckily, the beam didn't seem to harm Cassini, but future robotic and crewed missions should be wary of possible electric shocks from bodies in the solar system.

"Our observations show that this is also an important effect at outer planet moons, and that we need to take this into account when studying how these moons interact with their environment," Geraint Jones, a member of the Cassini Plasma Spectrometer instrument team who helped supervise the study, said in the same statement.
The $3.2 billion Cassini mission launched to space in 1997. The probe arrived at Saturn in 2004 and has been orbiting the gas giant ever since. Cassini is expected to continue studying Saturn and its moons until 2017, when the spacecraft will end its mission by intentionally plunging into the gas giant's atmosphere.

Wednesday, October 8, 2014

NGC 6823: Cloud Sculpting Star Cluster 
 Star cluster NGC 6823 is slowly turning gas clouds into stars. The center of the open cluster, visible on the upper right, formed only about two million years ago and is dominated in brightness by a host of bright young blue stars. Some outer parts of the cluster, visible in the featured image's center as the stars and pillars of emission nebula NGC 6820, contain even younger stars. The huge pillars of gas and dust likely get their elongated shape by erosion from hot radiation emitted from the brightest cluster stars. Striking dark globules of gas and dust are also visible across the upper left of the featured image. Open star cluster NGC 6823 spans about 50 light years and lies about 6000 light years away toward the constellation of the Fox (Vulpecula).