OrbitalHub

NASA dixit:

“October 18, 2009. Orbiting near the plane of Saturn’s rings, the Cassini spacecraft looks across the span of the rings to spy the small moon Epimetheus. The brightest spoke is visible on the left of the image, but others can be seen near the middle of the image and elsewhere on the B ring.

This view looks toward the northern, sunlit side of the rings from about 1 degree above the ringplane. Cassini is closer to the rings than to Epimetheus (113 kilometers, or 70 miles across). Two background stars are visible. The image was taken in visible light with the Cassini spacecraft narrow-angle camera. The view was acquired at a distance of approximately 2.2 million kilometers (1.4 million miles) from Epimetheus. Image scale is 13 kilometers (8 miles) 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.”

Image credit: NASA

NASA dixit:

“July 26, 2009. The Cassini spacecraft captured this image of a small object in the outer portion of Saturn’s B ring casting a shadow on the rings as Saturn approaches its August 2009 equinox. This new moonlet, situated about 300 miles (480 kilometers), inward from the outer edge of the B ring, was found by detection of its shadow which stretches 25 miles, or 41 kilometers, across the rings. The shadow length implies the moonlet is protruding about 660 feet, or 200 meters, above the ring plane. If the moonlet is orbiting in the same plane as the ring material surrounding it, which is likely, it must be about 1,300 feet, or 400 meters, across.

This object is not attended by a propeller feature, unlike the band of moonlets discovered in Saturn’s A ring earlier by Cassini. The A ring moonlets, which have not been directly imaged, were found because of the propeller-like narrow gaps on either side of them that they create as they orbit within the rings. The lack of a propeller feature surrounding the new moonlet is likely because the B ring is dense, and the ring material in a dense ring would be expected to fill in any gaps around the moonlet more quickly than in a less dense region like the mid-A ring. Also, it may simply be harder in the first place for a moonlet to create propeller-like gaps in a dense ring.

This image and others like it are only possible around the time of Saturn’s equinox which occurs every half-Saturn-year (equivalent to about 15 Earth years). The illumination geometry that accompanies equinox lowers the sun’s angle to the ring plane and causes out-of-plane structures to cast long shadows across the rings. This view looks toward the sunlit side of the rings from about 42 degrees below the ring plane. Background stars are visible on the right of the image. They appear elongated by the camera’s exposure time.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera. The view was obtained at a distance of approximately 296,000 kilometers (184,000 miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 120 degrees. Image scale is 1 kilometer (4,680 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.”

Image credit: NASA

NASA dixit:

“August 13, 2009. An unusually large propeller feature is detected just beyond the Encke Gap in this Cassini image of Saturn’s outer A ring taken a couple days after the planet’s August 2009 equinox.

The unique geometry of equinox has thrown into relief small moonlets within the rings and the structures they create around them. Propeller-like features, a few kilometers long, centered on and created by the action of small embedded moonlets only about 100 meters across, were discovered early in the mission. These previous findings constituted the first recognition of the presence in Saturn’s rings of bodies bigger than the largest ring particles (about 10 meters, or 30 feet, across) but smaller than the 8-kilometer-wide (5-mile-wide) ring moon, Daphnis, in the outer A ring.

From the 350-kilometer (220-mile) length of the shadow cast by this 130-kilometer-long (80-mile-long) propeller, the heights of these features above the ring plane have been measured to reach about 200 meters (650 feet), indicating the moonlet responsible for the propeller in this image is likely to be 400 meters (1,300 feet) across.

Cassini scientists have tracked several individual propeller moons embedded in Saturn’s A ring over several years. The A ring is the outermost of Saturn’s main rings. Imaging scientists nicknamed the propeller shown here “Earhart” after the American aviatrix Amelia Earhart.

It has since become a growing realization resulting from Cassini’s exploration of Saturn that the objects forming Saturn’s rings very likely span the full spectrum of sizes, from the smallest dust-sized ring particles to the ring-moons like Daphnis and 29-kilometer-wide (18-mile-wide) Pan — a significant advance in divining the origin of Saturn’s rings.

The novel illumination geometry that accompanies equinox lowers the sun’s angle to the ring plane, significantly darkens the rings, and causes out-of-plane structures to cast long shadows across the rings. (The rings have been brightened in this image to enhance visibility.) These scenes are possible only during the few months before and after Saturn’s equinox which occurs only once in about 15 Earth years.

This view looks toward the northern side of the rings from about 20 degrees above the ring plane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera. The view was acquired at a distance of approximately 1.2 million kilometers (746,000 miles) from Saturn and at a sun-Saturn-spacecraft, or phase, angle of 87 degrees. Image scale is 7 kilometers (4 miles) 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.”

Image credit: NASA

NASA dixit:

“On Mars, wind rules. Wind has been shaping the Red Planet’s landscapes for billions of years and continues to do so today. Studies using both a NASA orbiter and a rover reveal its effects on scales grand to tiny on the strangely structured landscapes within Gale Crater.

NASA’s Curiosity Mars rover, on the lower slope of Mount Sharp — a layered mountain inside the crater — has begun a second campaign of investigating active sand dunes on the mountain’s northwestern flank. The rover also has been observing whirlwinds carrying dust and checking how far the wind moves grains of sand in a single day’s time.

Gale Crater observations by NASA’s Mars Reconnaissance Orbiter have confirmed long-term patterns and rates of wind erosion that help explain the oddity of having a layered mountain in the middle of an impact crater.

“The orbiter perspective gives us the bigger picture — on all sides of Mount Sharp and the regional context for Gale Crater. We combine that with the local detail and ground-truth we get from the rover,” said Mackenzie Day of the University of Texas, Austin, lead author of a research report in the journal Icarus about wind’s dominant role at Gale.

The combined observations show that wind patterns in the crater today differ from when winds from the north removed the material that once filled the space between Mount Sharp and the crater rim. Now, Mount Sharp itself has become a major factor in determining local wind directions. Wind shaped the mountain; now the mountain shapes the wind.

The Martian atmosphere is about a hundred times thinner than Earth’s, so winds on Mars exert much less force than winds on Earth. Time is the factor that makes Martian winds so dominant in shaping the landscape. Most forces that shape Earth’s landscapes — water that erodes and moves sediments, tectonic activity that builds mountains and recycles the planet’s crust, active volcanism — haven’t influenced Mars much for billions of years. Sand transported by wind, even if infrequent, can whittle away Martian landscapes over that much time.”

Video credit: NASA Jet Propulsion Laboratory

NASA dixit:

“July 27, 2009. The novel illumination geometry created around the time of Saturn’s August 2009 equinox allows moons orbiting in or near the plane of Saturn’s equatorial rings to cast shadows onto the rings. These scenes are possible only during the few months before and after Saturn’s equinox, which occurs only once in about 15 Earth years.

Pan (28 kilometers, or 17 miles across) orbits in the Encke Gap. This view looks toward the unilluminated side of the rings from about 34 degrees above the ring plane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera. The view was acquired at a distance of approximately 839,000 kilometers (521,000 miles) from Pan and at a Sun-Pan-spacecraft, or phase, angle of 74 degrees. Image scale is 5 kilometers (3 miles) 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.”

Image credit: NASA

NASA dixit:

“February 12, 2009. Wendy Darling famously helped Peter Pan catch his shadow, and now Cassini captures the shadow of another Pan: Saturn’s 30-kilometer (19-mile) wide moon inhabiting the Encke Gap. In the center of this image, the shadow of Pan is a short streak thrown over the edge of the A ring where Pan travels its path through the Encke Gap.

One of the happy results of Saturn’s 29-year revolution around the sun is the changing elevation of the sun seen from the planet, and the changing elevation of the shadows of the rings and moons that the sun’s apparent motion brings. As Saturn approaches equinox, the angle at which the ringplane is inclined away from the sun will continue to decrease until August 2009, when equinox will bring about an alignment of the plane containing the rings with the rays of the sun. Only around the time of equinox is a moon’s shadow cast on the rings rather than the planet. Between now and equinox in August, the shadows cast by the moons on the rings will grow longer with time.

Cassini scientists planned a series of observations to chronicle these sights, knowing that the resulting images could hold valuable information about vertical displacements in the rings and the orbital inclinations of the shadow-casting moons. These planned images of course hold another reward: the simple but spectacular depiction of the path of sunlight across the solar system.

The image was taken in visible light with NASA’s Cassini spacecraft narrow-angle camera. This view looks toward the un-illuminated side of the rings from about 55 degrees above the ringplane. The view was obtained at a distance of approximately 997,000 kilometers (619,000 miles) from Pan and at a sun-Pan-spacecraft, or phase, angle of 112 degrees. Image scale is 6 kilometers (4 miles) 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.”

Image credit: NASA