Cassini’s Private Eclipse

For this movie, Cassini pointed its cameras toward Dione to witness its distant sibling moon Rhea briefly pass behind in a series of 32 individual frames taken over 17 minutes. Four individual frames from the eclipse are shown at bottom.

Rhea (1,528 kilometers, 949 miles across) is larger than Dione (1,123 kilometers, 698 miles across), but also is farther away as seen here – thus, the two moons appear to be roughly the same angular size.

The view shows principally the anti-Saturn side of Dione, and the Saturn-facing side of far-off Rhea.

Credit: NASA/JPL/Space Science Institute

Mimas Occults Janus

Icy, impact-riddled Mimas (396 kilometers, 246 miles across) slips briefly in front of the moon Janus (179 kilometers, 111 miles across) in this movie from Cassini.

The movie was created from 37 original images taken over the course of 20 minutes as the spacecraft’s narrow angle camera remained pointed toward Janus. Although Mimas moves a greater distance across the field of view, Janus also moved perceptibly during this time. The images were aligned to keep Janus close to the center of the scene. Additional frames were inserted between the 37 Cassini images in order to smooth the appearance of Mimas’ movement – a scheme called interpolation. Close-up images from the few minutes surrounding the occultation are arranged into a strip along the bottom of the GIF.

The terrain on Mimas seen here is about 80 degrees to the west of that visible in a previously released movie, which showed the little moon appearing to cross Saturn’s ring plane from Cassini’s vantage point. In that previous movie, the rim of the large impact crater Herschel (130 kilometers, 80 miles wide) was visible as a flattening of the moon’s eastern limb. In the new movie, Herschel is almost at dead center.

Contrast on Janus was mildly enhanced to aid the visibility of its surface. The right side of Mimas appears bright because the moon was partly overexposed in this image sequence.

Credit: NASA/JPL/Space Science Institute

Intense Color on Rhea

This intense false-color view highlights and enhances color variations across the intensely cratered and cracked surface of Rhea.

To create the false-color view, ultraviolet, green and infrared images were combined into a single black and white picture that isolates and maps regional color differences. This “color map” was then superposed over a clear-filter image. The origin of the color differences is not yet understood, but may be caused by subtle differences in the surface composition or the sizes of grains making up the icy soil.

Wispy markings were seen on the trailing hemispheres of both Rhea and Dione in images taken by the Voyager spacecraft, and were hypothesized by some researchers to be the result of material extruded onto the surface by ice volcanism. Cassini’s earlier revelation of the braided fractures on Dione led to speculation that Rhea’s wisps might also be created by fractures.

Credit: NASA/JPL/Space Science Institute

Neil deGrasse Tyson - We Stopped Dreaming

Scientists Bounce Laser Beams Off Old Soviet Moon Rover

Scientists have successfully bounced a laser off the Soviet Union’s old Lunokhod 1 rover, which trekked across the moon’s landscape more than four decades ago.

Lunokhod 1 was the first remote-controlled rover ever to land on another celestial body. The wheeled vehicle was carried to the lunar surface by a spacecraft called Luna 17, touching down in the Sea of Rains on Nov. 17, 1970.

Among its instruments, the rover toted a French-built laser retroreflector consisting of 14 corner cubes that can reflect laser light beamed from Earth. 

Attempts to contact the rover after the lunar night that began on Sept. 14, 1971, were unsuccessful, apparently due to a component failure on the rover. Lunokhod 1’s days of rambling around the moon formally ended on Oct. 4, 1971, after 11 lunar day-night cycles (322 Earth days).

The historical difficulty of ranging on Lunokhod 1 may have been due to a number of factors. The reflector may have been dusty, or its cover could have closed. Or the rover may not have been parked in view of Earth.

In the end, however, “it was more a problem of lack of confidence than to a technical difficulty,” Torre said.

Poor weather conditions prevented the scientists from getting a good determination of the Lunokhod 1 reflector’s efficiency. Still, the results have buoyed the interest of Earth-based scientists to continue beaming their lasers at the long-dead rover.

A retroreflector array was also left on the moon by the landing crew of NASA’s Apollo 11 mission in 1969, while two more retroreflector arrays were set up by Apollo 14 and Apollo 15 moonwalkers.

The final end-of-mission location of Lunokhod 1 was uncertain until 2010. But thanks to images snapped by NASA’s Lunar Reconnaissance Orbiter (LRO), both the Luna 17 lander and Lunokhod 1 were spotted.

Lunokhod 1 came to its final stop on a site situated around 1.4 miles (2.3 kilometers) north of its point of landing.

The success last month by the Grasse station was not the first laser ranging effort targeting the “lost” Lunokhod 1 reflector.

In April 2010, specialists at the Apache Point Observatory Lunar Laser-ranging Operation (APOLLO) in southern New Mexico used the LRO images to first pinpoint the locale of Lunokhod 1, closely enough for laser range measurements.

Surprisingly, the APOLLO researchers reported that the craft’s retroreflector was returning much more light than other reflectors on the moon.

Lunar laser ranging has been made possible by combining advances in laser technology, data processing and precision timing via atomic clocks, according to the International Laser Ranging Service, a service of the International Association of Geodesy.

Lunar laser ranging uses short-pulse lasers and state-of-the-art optical receivers and timing electronics to measure how long it takes light beamed from ground stations to travel to retroreflector arrays on the moon and back again.

It takes just two and a half seconds for light to make this roundtrip trek, requiring use of an atomic clock.

Because the reflectors on the moon are relatively small and a laser beam naturally loses its intensity with distance, only a tiny fraction of the signal makes it back. However, the information is sufficient for precise calculation of the Earth and moon’s movement: speed of rotation, axial variation and orbital deviation (taking into account, of course, the influence of other celestial bodies such as the sun).

Credit: SPACE.com

Keep An Eye Out For Thursday’s ‘Pink Moon’

If you glance up in the sky on Thursday, keep and eye out for the pink moon.

Named for the brilliant pink phlox that once signaled the arrival of Spring, the moon will be at its fullest at 3:57 p.m. EDT April 25.

First of all: No, it’s not pink

The spoiler is, Pink Moons are not really pink. It is simply the name for full moon that happens during the month of April — similar to February’s snow moon.

UPI.com reports that the moon might actually be slightly pink this year because of the lunar eclipse that’s set to happen in the afternoon.

So, why the name?

The “pink moon” name is part of a naming tradition traceable to Native American tribes. Full moons during different times of the year signaled changes in the seasons and other important dates (Farmer’s Almanac offers a handy breakdown).

Full Corn moon meant it was time to pick corn, Full Buck Moon shone at around the time of year deer bucks were sprouting antlers, and Full Sturgeon Moon probably coincided with sturgeon-fishing season.

Pink moon is so named because it occurred at around the time the plant wild ground phlox begins to blossom. Indigenous Americans took this as a sign that Spring had arrived.

But there will be a lunar eclipse, right?

Eh, sort of.

Some say that the Pink Moon may be especially worth stealing a glance this year, owing to the fact that it will coincide with a partial lunar eclipse. Those who live in Europe, parts of Asia or Africa will see the eclipse, says Space.com’s Joe Rao. North Americans, though are out of luck.

It is only a partial eclipse — people in Europe will see notice only a slight dark spot on the edge of the moon. You can watch the eclipse live stream at the Slooh Space Camera website.

A Moon Rise Over Los Angeles

Earlier this month, Los Angeles-based photographer Dan Marker-Moore pointed his Olympus OM-D EM-5 and a 100mm lens (equivalent to a 200mm in 35mm terms) at his city’s nighttime cityscape and photographed the rising of a full moon. He shot a series of photographs over half an hour, and then turned the photographs into three separate final pieces.

The first is the “time-slice” photograph, which shows multiple instances of the moon in a single frame (different “slices” of the photo are from different times).

Marker-Moore also took the entire sequence of photographs and turned them into this 10-second time-lapse video showing the moon emerging from the horizon as a dark, reddish circle and becoming whiter and brighter as it rises into the sky. Watch the video here

Finally, Marker-Moore took 11 of the photographs and turned them into this looping animated GIF showing the moon rising into the sky like some kind of celestial escalator:

You can find more of Marker-Moore’s work over on his website and Tumblr. He’s also the photographer behind the #payphoneography, which aims to preserve old payphones around the US as photos before they’re taken away forever.

NASA is planning for a robotic spaceship to lasso a small asteroid and park it near the moon for astronauts to explore

The robotic ship would capture the 500-ton 25-foot asteroid in 2019. Then using an Orion space capsule, now being developed, a crew of about four astronauts would nuzzle up next to the rock in 2021 for spacewalking exploration, according to a government document obtained by The Associated Press.

Yay!

Senator says NASA to lasso asteroid, bring it closer (Update)

NASA is planning for a robotic spaceship to lasso a small asteroid and park it near the moon for astronauts to explore, a top U.S. senator disclosed Friday. The robotic ship would capture the 500-ton 25-foot (450 metric ton, 7.6 meters) asteroid in 2019. Then using an Orion space capsule, now being developed, a crew of about four astronauts would nuzzle up next to the rock in 2021 for spacewalking exploration, according to a government document obtained by The Associated Press. Sen. Bill Nelson said the plan would speed up by four years the existing mission to land astronauts on an asteroid by bringing the space rock closer to Earth. Nelson, a Democrat who is chairman of the Senate science and space subcommittee, said Friday that President Barack Obama is putting $100 million in planning money for the accelerated asteroid mission in the 2014 budget that comes out next week. The money would be used to find the right small asteroid. “It really is a clever concept,” Nelson said in a news conference in Florida the state where NASA launches take place. “Go find your ideal candidate for an asteroid. Go get it robotically and bring it back.”

In this Jan. 13, 2013 file photo (above), the Orion Exploration Flight Test 1crew module is seen in the Operations and Checkout building during a media tour at the Kennedy Space Center in Cape Canaveral, Fla. Senate Science and Space subcommittee Chairman Sen. Bill Nelson, D-Fla. says President Barack Obama and NASA are planning for a robotic spaceship to lasso a small asteroid and park it near the moon. Then astronauts would explore it in 2021. Nelson said the plan would speed up by four years an existing mission to land astronauts on an asteroid by bringing the space rock closer to Earth. (AP Photo/John Raoux)

While there are thousands of asteroids that size out there, finding the right one that comes by Earth at just the right time to be captured will not be easy, said Donald Yeomans, who heads NASA’s Near Earth Object program that monitors close-by asteroids. He said once a suitable rock is found it would be captured with the space equivalent of “a baggie with a drawstring. You bag it. You attach the solar propulsion module to de-spin it and bring it back to where you want it.” Yeomans said a 25-foot asteroid is no threat to Earth because it would burn up should it inadvertently enter Earth’s atmosphere. The mission as Nelson described is perfectly safe, he said. Nelson said this would help NASA develop the capability to nudge away a dangerous asteroid if one headed to Earth in the future. It also would be training for a future mission to send astronauts to Mars in the 2030s, he said. The government document said the mission, with no price tag at the moment, would inspire because it “will send humans farther than they have ever been before.”

Galileo view of an Earth-Moon conjunction

As Galileo receded from its second flyby of Earth on December 16 and 17, 1992, it captured this sequence of Earth rotating as the Moon zipped by on its orbit. There are 56 frames in total, each separated by 15 minutes, spanning about 14 hours.

Credit: NASA / JPL / Doug Ellison

Thera Macula

Thera Macula, a slightly sunken region on Jupiter’s moon; Europa that may be where chaos terrain is actively being formed. These pictures are from the Galileo spacecraft, which orbited Jupiter for many years. The image below was produced using photoclinometry. The colors indicate topographic heights relative to background terrain. The centre of Thera Macula is sunken below the background terrain (denoted by pale green) by up to ~800 m just outside a large semi-circular northern subsiding province (NS), and shows evidence for thickening of matrix in its southern chaotic terrain (SC), which is elevated above the background terrain by up to ~800 m. Despite the distinct difference between the morphologies of the NS and the SC, they share a nearly continuous circular scarp boundary (red and black arrows), suggesting that they formed from a common subsurface disruption.

Blocks A, B and C are calving at reactivated pre-existing fractures. Within the NS, the platy-blocks appear bent, presumably by basal thinning and subsidence, and the edge of the NS appears ready to break or is being thinned (red arrow). Tall scarps (black arrows) either cast shadows (southern facing) within the region’s interior or have bright faces (northern facing), demonstrating the relatively low-lying nature of the centre of Thera Macula. To the lower right, an older band or ridge complex interrupted by the disruption of Thera Macula appears to be swelling along its ridge-like lineations, consistent with brine infiltration and refreeze (blue arrow). The still sunken topography of Thera Macula is indicative of subsurface water.

Credit: NASA/Nature

Io

Looking like a giant pizza covered with melted cheese and splotches of tomato and ripe olives, Io is the most volcanically active body in the solar system. Volcanic plumes rise 300 km (190 miles) above the surface, with material spewing out at nearly half the required escape velocity.

A bit larger than Earth’s Moon, Io is the third largest of Jupiter’s moons, and the fifth one in distance from the planet.

Although Io always points the same side toward Jupiter in its orbit around the giant planet, the large moons Europa and Ganymede perturb Io’s orbit into an irregularly elliptical one. Thus, in its widely varying distances from Jupiter, Io is subjected to tremendous tidal forces. These forces cause Io’s surface to bulge up and down (or in and out) by as much as 100 m (330 feet)! Compare these tides on Io’s solid surface to the tides on Earth’s oceans. On Earth, in the place where tides are highest, the difference between low and high tides is only 18 m (60 feet), and this is for water, not solid ground!

This tidal pumping generates a tremendous amount of heat within Io, keeping much of its subsurface crust in liquid form seeking any available escape route to the surface to relieve the pressure. Thus, the surface of Io is constantly renewing itself, filling in any impact craters with molten lava lakes and spreading smooth new floodplains of liquid rock. The composition of this material is not yet entirely clear, but theories suggest that it is largely molten sulfur and its compounds (which would account for the varigated coloring) or silicate rock (which would better account for the apparent temperatures, which may be too hot to be sulfur). Sulfur dioxide is the primary constituent of a thin atmosphere on Io. It has no water to speak of, unlike the other, colder Galilean moons. Data from the Galileo spacecraft indicates that an iron core may form Io’s center, thus giving Io its own magnetic field.

Io’s orbit, keeping it at more or less a cozy 422,000 km (262,000 miles) from Jupiter, cuts across the planet’s powerful magnetic lines of force, thus turning Io into a electric generator. Io can develop 400,000 volts across itself and create an electric current of 3 million amperes. This current takes the path of least resistance along Jupiter’s magnetic field lines to the planet’s surface, creating lightning in Jupiter’s upper atmosphere.

As Jupiter rotates, it takes its magnetic field around with it, sweeping past Io and stripping off about 1,000 kg (1 ton) of Io’s material every second! This material becomes ionized in the magnetic field and forms a doughnut-shaped cloud of intense radiation referred to as a plasma torus. Some of the ions are pulled into Jupiter’s atmosphere along the magnetic lines of force and create auroras in the planet’s upper atmosphere. It is the ions escaping from this torus that inflate Jupiter’s magnetosphere to over twice the size we would expect.

Discovery:
Io was discovered on 8 January 1610 by Galileo Galilei. The discovery, along with three other Jovian moons, was the first time a moon was discovered orbiting a planet other than Earth. The discovery of the four Galilean satellites eventually led to the understanding that planets in our solar system orbit the sun, instead of our solar system revolving around Earth. Galileo apparently had observed Io on 7 January 1610, but had been unable to differentiate between Io and Europa until the next night.

How Io Got its Name:
Galileo originally called Jupiter’s moons the Medicean planets, after the Medici family and referred to the individual moons numerically as I, II, III, and IV. Galileo’s naming system would be used for a couple of centuries.

It wouldn’t be until the mid-1800s that the names of the Galilean moons, Io, Europa, Ganymede, and Callisto, would be officially adopted, and only after it became apparent that naming moons by number would be very confusing as new additional moons were being discovered.

Io was originally designated Jupiter I by Galileo because it is the first satellite of Jupiter. Io is named for the daughter of Inachus, who was raped by Jupiter. Jupiter, in an effort to hide his crime from his wife, Juno, transformed Io into a heifer.

Credit: NASA/JPL

Iapetus Spins and Tilts

Saturn’s two-faced moon tilts and rotates for Cassini in this mesmerizing movie sequence of images acquired during the spacecraft’s close encounter with Iapetus on November 12, 2005.

The encounter begins with Cassini about 850,000 kilometers (530,000 miles) distant from Iapetus. Cassini approached over the moon’s northern hemisphere, allowing for excellent full views of a 575-kilometer (360-mile) wide impact basin in northeastern Cassini Regio. Astronomer Giovanni Cassini discovered the light/dark dichotomy of Iapetus’ two hemispheres (among his other Saturn discoveries), and the dark region – as well as the spacecraft – bears his name.

Also prominent in these images is a 380-kilometer (235-mile) wide basin to the northwest of the larger basin, in the transition zone between Cassini Regio and a brighter region called Roncevaux Terra, with its 150-kilometer (95-mile) wide crater Roland (at top, with a prominent central peak).

The movie takes Cassini to its closest approach, at about 415,000 kilometers (260,000 miles) from Iapetus, then looks back at the moon’s receding crescent. The sequence ends with Cassini at a distance of about 460,000 kilometers (285,000 miles) from the moon.

Iapetus is 1,471 kilometers (914 miles) across.

Images taken using ultraviolet, green and infrared spectral filters in the narrow-angle camera were combined to create false-color frames for this movie. The color seen here is similar to that produced in (red, green and blue) natural color views. Resolution in the original images taken at closest approach to Iapetus was about 3 kilometers (2 miles) per pixel. The color frames were resized to create the movie.

Credit: NASA/JPL/Space Science Institute

Intense Color on Rhea

These intense false-color views highlight and enhance color variations across the intensely cratered and cracked surface of Rhea.

To create the false-color view, ultraviolet, green and infrared images were combined into a single black and white picture that isolates and maps regional color differences. Most of the large-scale variations in brightness across the surface are removed by this process. This “color map” was then superposed over a clear-filter image.

The origin of the color differences is not yet understood, but may be caused by subtle differences in the surface composition or the sizes of grains making up the icy soil.

Wispy markings were seen on the trailing hemispheres of both Rhea and Dione in images taken by the Voyager spacecraft, and were hypothesized by some researchers to be the result of material extruded onto the surface by ice volcanism. Cassini’s earlier revelation of the braided fractures on Dione led to speculation that Rhea’s wisps might also be created by fractures.

Credit: NASA/JPL/Space Science Institute

Enceladus to Scale

Enceladus is only 504 kilometers (313 miles) across, small enough to fit within the length of the United Kingdom, as illustrated here.

(The intriguing icy moon also could fit comfortably within the states of Arizona or Colorado.)

Credit: NASA/JPL/Space Science Institute