OrbitalHub

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

NASA dixit:

“July 26, 2009. The Cassini spacecraft eyes a prominent crater on the moon Janus. The south pole lies on the terminator at the bottom left of the image. This view is centered on terrain at 16 degrees south latitude, 64 degrees west longitude. This view looks toward the leading hemisphere of Janus (179 kilometers, or 111 miles across). North on Janus is up and rotated 31 degrees to the right. The image was taken in visible light with the Cassini spacecraft narrow-angle camera. The view was acquired at a distance of approximately 98,000 kilometers (61,000 miles) from Janus and at a Sun-Janus-spacecraft, or phase, angle of 58 degrees. Image scale is 586 meters (1,922 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

ESA dixit:

“The ExoMars Rover, developed by ESA, provides key mission capabilities: surface mobility, subsurface drilling and automatic sample collection, processing, and distribution to instruments. It hosts a suite of analytical instruments dedicated to exobiology and geochemistry research: this is the Pasteur payload.

The Rover uses solar panels to generate the required electrical power, and is designed to survive the cold Martian nights with the help of novel batteries and heater units. Due to the infrequent communication opportunities, only 1 or 2 short sessions per sol (Martian day), the ExoMars Rover is highly autonomous. Scientists on Earth will designate target destinations on the basis of compressed stereo images acquired by the cameras mounted on the Rover mast.

The Rover must then calculate navigation solutions and safely travel approximately 100 m per sol. To achieve this, it creates digital maps from navigation stereo cameras and computes a suitable trajectory. Close-up collision avoidance cameras are used to ensure safety.

The locomotion is achieved through six wheels. Each wheel pair is suspended on an independently pivoted bogie (the articulated assembly holding the wheel drives), and each wheel can be independently steered and driven. All wheels can be individually pivoted to adjust the Rover height and angle with respect to the local surface, and to create a sort of walking ability, particularly useful in soft, non-cohesive soils like dunes. In addition, inclinometers and gyroscopes are used to enhance the motion control robustness. Finally, Sun sensors are utilised to determine the Rover’s absolute attitude on the Martian surface and the direction to Earth.

The camera system’s images, combined with ground penetrating radar data collected while travelling, will allow scientists on-ground to define suitable drilling locations.The Rover subsurface sampling device will then autonomously drill to the required depth (maximum 2 m) while investigating the borehole wall mineralogy, and collect a small sample. This sample will be delivered to the analytical laboratory in the heart of the vehicle. The laboratory hosts four different instruments and several support mechanisms. The sample will be crushed into a fine powder. By means of a dosing station the powder will then be presented to other instruments for performing a detailed chemistry, physical, and spectral analyses.”

Video credit: ESA