Starship Asterisk*

ttp://earthobservatory.nasa.gov/IOTD/view.php?id=50666 wrote:

Valles Caldera

---

<<Spanning about 22 kilometers (14 miles), Valles Caldera in New Mexico was formed from the collapse of a magma chamber following ancient volcanic eruptions. The Enhanced Thematic Mapper Plus on Landsat 7 satellite captured this natural-color image of the area on May 22, 2002. Plants have colonized parts of the caldera, which is surrounded by a network of valleys. The city of Los Alamos lies to the east.

Valles Caldera is a complex formation resulting from two high-volume eruptions that occurred during the Pleistocene Epoch. Eruptions about 1.7 million and 1.2 million years ago pushed up magma that was rich with water and granite. When the magma broke through overlying rock layers, its water content turned to steam, driving powerful eruptions that buried the surrounding area in layers of volcanic ash—hundreds of meters thick in some places. As ash and steam billowed overhead, magma under the surface dwindled. In the eruption 1.2 million years ago, a giant rock plug descended into the magma chamber, leaving steep rock walls around its perimeter. Landslides toward the chamber quickly followed. Over thousands of years, however, the caldera floor slowly rose. Today, hot springs and fumaroles persist at Valles Caldera. The volcanic ash that sprayed over the landscape during the Pleistocene later hardened into the Bandelier Tuff. Parts of this porous volcanic rock later became home to Ancestral Pueblo people who carved cavates. Some of these ancient dwellings are now preserved at Bandelier National Monument.>>

http://www.planetaryexploration.net/jupiter/io/loki.html wrote:

<<Loki is the most powerful volcano in the solar system, and consistently emits more heat than all of Earth's volcanoes combined. Loki has an enormous caldera, larger than the state of Maryland, which is continually flooded with lava. Lava temperatures recorded at the Loki hot spot are similar to those of basaltic lavas on Earth.

Active lava and lava that is still cooling cover the floor of the Loki caldera and surround a light-colored island. With the exception of a narrow crack in the center of the island where high temperatures indicate volcanic activity, the rest of the island appears to be cold. Current volcanic activity can be seen in this temperature map. The yellow regions correspond to temperatures of about 87 degrees Celsius, and the red areas record temperatures of about 157 degrees Celsius. The hottest temperatures correspond to the white areas. Here temperatures reach upwards of 567 degrees Celsius.

Scientists are still trying to determine what kind of volcano Loki is. The high temperatures on the western edge of the caldera support the idea that it is an active lava lake with molten material beneath the crust. In volcanic calderas on Earth, such as Hawaii's Kilauea volcano, the crust that forms on the surface as the lava cools tends to drift outward, eventually hitting the caldera wall. Upon striking the wall, the crust breaks up causing hotter material from below the surface to be exposed. >>

Boomer12k wrote:
I wonder if Jupiter's Ring comes from some of this material, like Saturn's Ring coming from Enceladus.

http://en.wikipedia.org/wiki/Rings_of_Jupiter wrote:

A schema of Jupiter's ring system showing the four main components

---

The upper image shows the main ring in back-scattered light as seen by the New Horizons spacecraft. The fine structure of its outer part is visible. The lower image shows the main ring in forward-scattered light demonstrating its lack of any structure except the Metis notch.

---

<<The planet Jupiter has a system of rings, known as the rings of Jupiter or the Jovian ring system. It was the third ring system to be discovered in the Solar System, after those of Saturn and Uranus. It was first observed in 1979 by the Voyager 1 space probe and thoroughly investigated in the 1990s by the Galileo orbiter. It has also been observed by the Hubble Space Telescope and from Earth for the past 23 years. Ground-based observations of the rings require the largest available telescopes.

The Jovian ring system is faint and consists mainly of dust. It has four main components: a thick inner torus of particles known as the "halo ring"; a relatively bright, exceptionally thin "main ring"; and two wide, thick and faint outer "gossamer rings", named for the moons of whose material they are composed: Amalthea and Thebe.

The main and halo rings consist of dust ejected from the moons Metis, Adrastea and other unobserved parent bodies as the result of high-velocity impacts. High-resolution images obtained in February and March 2007 by the New Horizons spacecraft revealed a rich fine structure in the main ring.

In visible and near-infrared light, the rings have a reddish color, except the halo ring, which is neutral or blue in color. The size of the dust in the rings varies, but the cross-sectional area is greatest for nonspherical particles of radius about 15 μm in all rings except the halo. The halo ring is probably dominated by submicrometre dust.

The dust is constantly being removed from the main ring by a combination of Poynting–Robertson drag and electromagnetic forces from the Jovian magnetosphere. Volatile materials, for example ices, evaporate quickly. The lifetime of dust particles in the ring is from 100 to 1000 years, so the dust must be continuously replenished in the collisions between large bodies with sizes from 1 cm to 0.5 km and between the same large bodies and high velocity particles coming from outside the Jovian system. This parent body population is confined to the narrow—about 1000 km—and bright outer part of the main ring, and includes Metis and Adrastea. The largest parent bodies must be less than 0.5 km in size. The upper limit on their size was obtained by New Horizons spacecraft. The previous upper limit, obtained from HST and Cassini observations, was near 4 km. The dust produced in collisions retains approximately the same orbital elements as the parent bodies and slowly spirals in the direction of Jupiter forming the faint (in back-scattered light) innermost part of the main ring and halo ring. The age of the main ring is currently unknown, but it may be the last remnant of a past population of small bodies near Jupiter.

Images from the Galileo and New Horizons space probes show the presence of two sets of spiraling vertical corrugations in the main ring. These waves became more tightly wound over time at the rate expected for differential nodal regression in Jupiter's gravity field. Extrapolating backwards, the more prominent of the two sets of waves is appears to have been excited in 1995, around the time of the impact of Comet Shoemaker-Levy 9 with Jupiter, while the smaller set appears to date to the first half of 1990.>>

kwaj87 wrote:Why are there never any stars in pictures such as these?