“October 16, 2010. NASA’s Cassini spacecraft obtained this raw image of the moon Mimas just before Mimas went into shadow behind Saturn. The camera was approximately 101,552 kilometers (63,1010 miles) away.”
“After almost 20 years in space, NASA’s Cassini spacecraft begins the final chapter of its remarkable story of exploration: its Grand Finale. Between April and September 2017, Cassini will undertake a daring set of orbits that is, in many ways, like a whole new mission. Following a final close flyby of Saturn’s moon Titan, Cassini will leap over the planet’s icy rings and begin a series of 22 weekly dives between the planet and the rings.
No other mission has ever explored this unique region. What we learn from these final orbits will help to improve our understanding of how giant planets – and planetary systems everywhere – form and evolve.
On the final orbit, Cassini will plunge into Saturn’s atmosphere, sending back new and unique science to the very end. After losing contact with Earth, the spacecraft will burn up like a meteor, becoming part of the planet itself.
Cassini’s Grand Finale is about so much more than the spacecraft’s final dive into Saturn. That dramatic event is the capstone of six months of daring exploration and scientific discovery. And those six months are the thrilling final chapter in a historic 20-year journey.”
“The 8.5-minute test conducted at NASA’s Stennis Space Center is part of a series of tests designed to put the upgraded former space shuttle engines through the rigorous temperature and pressure conditions they will experience during a launch. The tests also support the development of a new controller, or “brain,†for the engine, which monitors engine status and communicates between the rocket and the engine, relaying commands to the engine and transmitting data back to the rocket.”
“August 13, 2010. Small water ice particles fly from fissures in the south polar region of Saturn’s moon Enceladus in this image taken during the flyby of the moon by NASA’s Cassini spacecraft. This view looks toward the night side of Saturn, which is in the lower left of the image. Enceladus, in the top right, is closer to the spacecraft than the planet is in this view. Sunlight scatters through the planet’s atmosphere and forms the bright diagonal line running from the left to bottom right of the image. The atmosphere appears layered here. Scientists think the different layers on the limb are real and not an artifact of the camera’s exposure.
The famous jets, imaged by Cassini’s cameras for the first time in 2005, are faintly seen here erupting from the fractures that cross the south polar region of the moon. Illuminated terrain seen on Enceladus is on the leading hemisphere of the moon, or the side facing forward in the moon’s orbit around Saturn. North on Enceladus (504 kilometers, 313 miles across) is up. The jets appear faint here, but can be seen near the center of the image.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera. The view was obtained at a distance of approximately 59,000 kilometers (37,000 miles) from Enceladus and at a sun-Enceladus-spacecraft, or phase, angle of 155 degrees. Image scale on Enceladus is 353 meters (1,157 feet) per pixel.”
“After almost 20 years in space, NASA’s Cassini spacecraft begins the final chapter of its remarkable story of exploration: its Grand Finale. Between April and September 2017, Cassini will undertake a daring set of orbits that is, in many ways, like a whole new mission. Following a final close flyby of Saturn’s moon Titan, Cassini will leap over the planet’s icy rings and begin a series of 22 weekly dives between the planet and the rings.
No other mission has ever explored this unique region. What we learn from these final orbits will help to improve our understanding of how giant planets – and planetary systems everywhere – form and evolve.
On the final orbit, Cassini will plunge into Saturn’s atmosphere, sending back new and unique science to the very end. After losing contact with Earth, the spacecraft will burn up like a meteor, becoming part of the planet itself.
Cassini’s Grand Finale is about so much more than the spacecraft’s final dive into Saturn. That dramatic event is the capstone of six months of daring exploration and scientific discovery. And those six months are the thrilling final chapter in a historic 20-year journey.”
“Gale is a crater, and probable dry lake, on Mars near the northwestern part of the Aeolis quadrangle at 5.4°S 137.8°E. It is 154 km (96 mi) in diameter and estimated to be about 3.5-3.8 billion years old. The crater was named after Walter Frederick Gale, an amateur astronomer from Sydney, Australia, who observed Mars in the late 19th century. Aeolis Mons is a mountain in the center of Gale and rises 5.5 km (18,000 ft) high. Aeolis Palus is the plain between the northern wall of Gale and the northern foothills of Aeolis Mons. Peace Vallis, a nearby outflow channel, ‘flows’ down from the Gale crater hills to the Aeolis Palus below and seems to have been carved by flowing water. The NASA Mars rover, Curiosity, of the Mars Science Laboratory (MSL) mission, landed in “Yellowknife” Quad 51 of Aeolis Palus in Gale at 05:32 UTC August 6, 2012. NASA named the landing location Bradbury Landing on August 22, 2012. Curiosity is exploring Aeolis Mons and surrounding areas.
Gale crater, named for Walter F. Gale (1865-1945), an amateur astronomer from Australia, spans 154 km (96 mi) in diameter and holds a mountain, Aeolis Mons (informally named “Mount Sharp” to pay tribute to geologist Robert P. Sharp) rising 18,000 ft (5,500 m) from the crater floor, higher than Mount Rainier rises above Seattle. Gale is roughly the size of Connecticut and Rhode Island.
The crater formed when a meteor hit Mars in its early history, about 3.5 to 3.8 billion years ago. The meteor impact punched a hole in the terrain, and the subsequent explosion ejected rocks and soil that landed around the crater. Layering in the central mound (Aeolis Mons) suggests it is the surviving remnant of an extensive sequence of deposits. Some scientists believe the crater filled in with sediments and, over time, the relentless Martian winds carved Aeolis Mons, which today rises about 5.5 km (3.4 mi) above the floor of Gale—three times higher than the Grand Canyon is deep.
At 10:32 p.m. PDT on Aug. 5, 2012 (1:32 a.m. EDT on Aug. 6, 2012), the Mars Science Laboratory rover, Curiosity, landed on Mars at 4.5°S 137.4°E, at the foot of the layered mountain inside Gale crater. Curiosity landed within a landing ellipse approximately 7 km (4.3 mi) by 20 km (12 mi). The landing ellipse is about 4,400 m (14,400 ft) below Martian “sea level” (defined as the average elevation around the equator). The expected near-surface atmospheric temperatures at the landing site during Curiosity’s primary mission (1 Martian year or 687 Earth days) are from −90 °C (−130 °F) to 0 °C (32 °F).
Scientists chose Gale as the landing site for Curiosity because it has many signs that water was present over its history. The crater’s geology is notable for containing both clays and sulfate minerals, which form in water under different conditions and may also preserve signs of past life. The history of water at Gale, as recorded in its rocks, is giving Curiosity lots of clues to study as it pieces together whether Mars ever could have been a habitat for microbes. Gale Crater contains a number of fans and deltas that provide information about lake levels in the past, including: Pancake Delta, Western Delta, Farah Vallis delta and the Peace Vallis Fan.”
“August 13, 2010. This dramatic view looks across the region of Enceladus’ geyser basin and down on the ends of the Baghdad and Damascus fractures that face Saturn. The image, which looks approximately in the direction of Saturn, was taken from a more elevated viewpoint than other Cassini survey images of this area of the moon’s south pole. The geysering segments of the fractures seen here are among the most active and warmest in the whole region. As seen from the spacecraft from an elevation angle of 25 degrees south, the jets are projected against the bright surface as opposed to black sky. Consequently, despite the pronounced activity, the jets appear fuzzy, or indistinct, in this image and their tilts are consequently not measurable. Though their source locations are clearly seen, this image was not used in the process of triangulation, but instead it was used to confirm source locations determined from triangulation using other images.
The image was taken with Cassini’s narrow-angle camera through the clear filter, with an image scale about 230 feet (70 meters) per pixel and a sun-Enceladus-spacecraft, or phase, angle of about 151 degrees.”
“After almost 20 years in space, NASA’s Cassini spacecraft begins the final chapter of its remarkable story of exploration: its Grand Finale. Between April and September 2017, Cassini will undertake a daring set of orbits that is, in many ways, like a whole new mission. Following a final close flyby of Saturn’s moon Titan, Cassini will leap over the planet’s icy rings and begin a series of 22 weekly dives between the planet and the rings.
No other mission has ever explored this unique region. What we learn from these final orbits will help to improve our understanding of how giant planets – and planetary systems everywhere – form and evolve.
On the final orbit, Cassini will plunge into Saturn’s atmosphere, sending back new and unique science to the very end. After losing contact with Earth, the spacecraft will burn up like a meteor, becoming part of the planet itself.
Cassini’s Grand Finale is about so much more than the spacecraft’s final dive into Saturn. That dramatic event is the capstone of six months of daring exploration and scientific discovery. And those six months are the thrilling final chapter in a historic 20-year journey.”
“Sunspots are temporary phenomena on the Sun’s photosphere that appear as spots darker than the surrounding areas. They are regions of reduced surface temperature caused by concentrations of magnetic field flux that inhibit convection. Sunspots usually appear in pairs of opposite magnetic polarity. Their number varies according to the approximately 11-year solar cycle. Individual sunspots may last anywhere from a few days to a few months, but eventually decay. Sunspots expand and contract as they move across the surface of the Sun, with diameters ranging from 16 km (10 mi) to 160,000 km (100,000 mi). The larger variety are visible from Earth without the aid of a telescope. They may travel at relative speeds, or proper motions, of a few hundred meters per second when they first emerge.
Indicating intense magnetic activity, sunspots accompany secondary phenomena such as coronal loops, prominences, and reconnection events. Most solar flares and coronal mass ejections originate in magnetically active regions around visible sunspot groupings. Similar phenomena indirectly observed on stars other than the Sun are commonly called starspots, and both light and dark spots have been measured.
Although they are at temperatures of roughly 3,000–4,500 K (2,700–4,200 °C), the contrast with the surrounding material at about 5,780 K (5,500 °C) leaves sunspots clearly visible as dark spots. This is because the luminance (which is essentially “brightness” in visible light) of a heated black body (closely approximated by the photosphere) at these temperatures varies extremely with temperature—considerably more so than the (temperature to the fourth power) variation in the total black-body radiation at all wavelengths (see Stefan–Boltzmann law). Isolated from the surrounding photosphere a sunspot would be brighter than the Moon.
Sunspots have two parts: the central umbra, which is the darkest part, where the magnetic field is approximately vertical (normal to the Sun’s surface) and the surrounding penumbra, which is lighter, where the magnetic field is more inclined.
Although the details of sunspot generation are still a matter of research, it appears that sunspots are the visible counterparts of magnetic flux tubes in the Sun’s convective zone that get “wound up” by differential rotation. If the stress on the tubes reaches a certain limit, they curl up and puncture the Sun’s surface. Convection is inhibited at the puncture points; the energy flux from the Sun’s interior decreases; and with it surface temperature.
The Wilson effect implies that sunspots are depressions on the Sun’s surface. Observations using the Zeeman effect show that prototypical sunspots come in pairs with opposite magnetic polarity. From cycle to cycle, the polarities of leading and trailing (with respect to the solar rotation) sunspots change from north/south to south/north and back. Sunspots usually appear in groups.
Magnetic pressure should tend to remove field concentrations, causing the sunspots to disperse, but sunspot lifetimes are measured in days to weeks. In 2001, observations from the Solar and Heliospheric Observatory (SOHO) using sound waves traveling below the photosphere (local helioseismology) were used to develop a three-dimensional image of the internal structure below sunspots; these observations show that a powerful downdraft underneath each sunspot, forms a rotating vortex that sustains the concentrated magnetic field.”
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