The Solar System. Titan (Saturn).
This is the first coloured view of Titan's surface, following processing to add reflection spectra data, gives a better indication of the actual colour of the surface. Initially thought to be rocks or ice blocks, they are more pebble-sized. The two rock-like objects just below the middle of the image are about 15 centimetres (left) and 4 centimetres (centre) across respectively, at a distance of about 85 centimetres from Huygens. The surface is darker than originally expected, consisting of a mixture of water and hydrocarbon ice. There is also evidence of erosion at the base of these objects, indicating possible fluvial activity.
It appears that Huygens may have landed in a dry riverbed. However, the liquid that flowed here was not water but methane. Spectra measurements (colour) are consistent with a composition of dirty water ice rather than silicate rocks. However, these are rock-like solid at Titan's temperatures.
Titan's soil appears to consist at least in part of precipitated deposits of the organic haze that shrouds the planet. This dark material settles out of the atmosphere. When washed off high elevations by methane rain, it concentrates at the bottom of the drainage channels and riverbeds contributing to the dark areas seen in DISR images.
Images captured by the DISR reveal that Titan has extraordinarily Earth-like meteorology and geology. Images show a complex network of narrow drainage channels running from brighter highlands to lower, flatter, dark regions. These channels merge into river systems running into lakebeds featuring offshore "islands" and "shoals" remarkably similar to those on Earth.
Other Huygens' data provide strong evidence for liquids flowing on Titan. However, the fluid involved is methane, a simple organic compound that can exist as a liquid or gas at Titan's sub-170 degree C temperatures, rather than water as on Earth. Titan's rivers and lakes appear dry at the moment, but rain may have occurred not long ago.
A single image from the Huygens DISR instrument of a dark plain area on Titan, seen during descent to the landing site, that indicates flow around bright 'islands'. The areas below and above the bright islands may be at different elevations.
A single Huygens DISR image that shows two new features on the surface of Titan. A bright linear feature suggests an area where water ice may have been extruded onto the surface. Also visible are short, stubby dark channels that may have been formed by 'springs' of liquid methane rather than methane 'rain'.
This picture is a composite of 30 images from ESA's Huygens probe. They were taken from an altitude varying from 13 kilometres down to 8 kilometres when the probe was descending towards its landing site. These images were taken with a resolution of about 20 metres per pixel and cover an area extending out to 30 kilometres.
This image, taken during the Huygens descent to the surface of Titan, shows the boundary between the lighter-coloured uplifted terrain, marked with what appear to be drainage channels, and darker lower areas. These images were taken from an altitude of about 8 kilometres with a resolution of about 20 metres per pixel.
Composite of Titan's surface seen during descent. It shows a full 360-degree view around Huygens. The left-hand side, behind Huygens, shows a boundary between light and dark areas. The white streaks seen near this boundary could be ground 'fog' of methane or ethane vapour, as they were not immediately visible from higher altitudes. As the probe descended, it drifted over a plateau (centre of image) and was heading towards its landing site in a dark area (right). This dark area is possibly a drainage channel which might still contain liquid material. From the drift of the probe, the wind speed has been estimated at around 6-7 metres per second. These images were taken from an altitude of about 8 kilometres with a resolution of about 20 metres per pixel.
This is one of the first raw images returned by the ESA Huygens probe during its successful descent. It was taken from an altitude of 16.2 kilometres with a resolution of approximately 40 metres per pixel. It apparently shows short, stubby drainage channels leading to a shoreline.
This is one of the first raw images returned by the ESA Huygens probe during its successful descent.It was taken at an altitude of 8 kilometres with a resolution of 20 metres per pixel. It shows what could be the landing site, with shorelines and boundaries between raised ground and flooded plains.
The image depicts the first moments after Deep Impact's probe interfaced with comet Tempel 1. The illuminated -- and possibly incandescent -- debris is expanding from the impact site. The rough-hewn edges at the top and bottom of the flash are a result of light given off at impact saturating some of the pixels in the camera's imager. The pixels "bleed" excess electronic charge onto adjacent pixels in the same column. This image was taken by Deep Impact's high-resolution camera. Image credit: NASA/JPL-Caltech/UMD
Deep Impact, Comet Tempel 1 (7/2005)
This movie shows Deep Impact's impactor probe approaching comet Tempel 1. It is made up of images taken by the probe's impactor targeting sensor. The probe collided with the comet at 10:52 p.m. Pacific time, July 3 (1:52 a.m. Eastern time, July 4). Image credit: NASA/JPL-Caltech/UMD
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When NASA's Deep Impact probe collided with Tempel 1, a bright, small flash was created, which rapidly expanded above the surface of the comet. This flash lasted for more than a second. Its overall brightness is close to that predicted by several models. After the initial flash, there was a pause before a bright plume quickly extended above the comet surface. The debris from the impact eventually cast a long shadow across the surface, indicating a narrow plume of ejected material, rather than a wide cone. The Deep Impact probe appears to have struck deep, before gases were heated and explosively released. The impact crater was observed to grow in size over time. A preliminary interpretation of these data indicate that the upper surface of the comet may be fluffy, or highly porous. The observed sequence of impact events is similar to laboratory experiments using highly porous targets, especially those that are rich in volatile substances. The duration of the hot, luminous gas phase, as well as the continued growth of the crater over time, all point to a model consistent with a large crater. This image was taken by Deep Impact's medium-resolution camera. Image credit: NASA/JPL-Caltech/UMD
Voyager hits the edge of the sun’s influence, moving to interstellar space (2005). Voyager has been in space for 27 years.
To envision the Sun's presence in the Milky Way galaxy, think of a ship plowing through the ocean, being tossed by currents. As the ship sails ahead, a bow shock spreads around the vessel. The area under the Sun's influence, stretching well beyond the planets and forming what's called the heliosphere, is like a ship. The outer edges of the heliosphere are gently buffeted by interstellar wind, the gas and dust between the stars. As the Sun orbits the center of the Milky Way galaxy, the heliosphere moves as well, creating a bow shock ahead of it in interstellar space. Termination Shock:Blowing outward billions of kilometers from the Sun is the solar wind, a thin stream of electrically charged gas. This wind travels at an average speed ranging from 300 to 700 kilometers per second (700,000 - 1,500,000 miles per hour) until it reaches the termination shock. At this point, the speed of the solar wind drops abruptly as it begins to feel the effects of interstellar wind. Heliosphere:The solar wind, emanating from the Sun, creates a bubble that extends far past the orbits of the planets. This bubble is the heliosphere, shaped like a long wind sock as it moves with the Sun through interstellar space. Heliosheath:The heliosheath is the outer region of the heliosphere. Voyager entered the heliosheath about 14 billion kilometers (approximately 8.7 billion miles) from the Sun. This is about 94 times the distance from the Sun to Earth. The heliosheath is just beyond the termination shock, the point where the solar wind slows abruptly, becoming denser and hotter. The solar wind piles up as it presses outward against the approaching wind in interstellar space. Heliopause:The boundary between solar wind and interstellar wind is the heliopause, where the pressure of the two winds are in balance. This balance in pressure causes the solar wind to turn back and flow down the tail of the heliosphere. Once Voyager passes the heliopause, it will be in interstellar space. Bow shock:As the heliosphere plows through interstellar space, a bow shock forms, much as forms in front of a boulder in a stream. Voyager 2:Voyager 2 has visited more planets than any other spacecraft, swinging by Jupiter, Saturn, Uranus and Neptune. Voyager 2 was deflected downward by Neptune and is heading southward below the plane of the planets. With a somewhat lower speed than Voyager 1, it is about eighty percent as far from the Sun. Voyager 1:Voyager 1 is the most distant human-made object in the universe, At the beginning of 2005, the spacecraft was about 94 times as far from the Sun as is Earth. It was deflected northward above the plane of the planets' orbits when it swung by Saturn in 1980 and is now speeding outward from the Sun at nearly one million miles per day, a rate that would take it from Los Angeles to New York in less than four minutes. Long-lived nuclear batteries are expected to provide electrical power until at least 2020 when Voyager 1 will be more than 13 billion miles from Earth and may have reached interstellar space. Image Credit: NASA/Walt Feimer