Stardust (by PostPanic)

From Dutch designer and director Mischa Rozema comes Stardust — a breathtaking short film based on a combination of real NASA footage and science fiction imagery, celebrating the legacy of the Voyager 1 and inspired by Dutch graphic designer Arjan Groot, who passed away from cancer at the age of 39.

[Brainpickings]

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Backing Up From Earth

“The Earth is a small stage, in the vast cosmic arena” - Carl Sagan

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Rain is Falling from Saturn’s Rings

Astronomers have known for years there was water in Saturn’s upper atmosphere, but they weren’t sure exactly where it was coming from. New observations have found water is raining down on Saturn, and it is coming from the planet’s rings.

“Saturn is the first planet to show significant interaction between its atmosphere and ring system,” said James O’Donoghue, a postgraduate researcher at the University of Leicester and author of a new paper published in the journal Nature. “The main effect of ring rain is that it acts to ‘quench’ the ionosphere of Saturn, severely reducing the electron densities in regions in which it falls.”

Using the Keck Observatory, O’Donoghue and a team of researchers found charged water particles falling from the planet’s rings into Saturn’s atmosphere. They also found the extent of the ring-rain is far greater, and falls across larger areas of the planet, than previously thought. The work reveals the rain influences the composition and temperature structure of parts of Saturn’s upper atmosphere.

O’Donoghue said the ring’s effect on electron densities is important because it explains why, for many decades, observations have shown electron densities to be unusually low at some latitudes at Saturn.

“It turns out a major driver of Saturn’s ionospheric environment and climate across vast reaches of the planet are ring particles located 120,000 miles [200,000 kilometers] overhead,” said Kevin Baines, a co-author on the paper, from the Jet Propulsion Laboratory. “The ring particles affect which species of particles are in this part of the atmospheric temperature.”

In the early 1980s, images from NASA’s Voyager spacecraft showed two to three dark bands on Saturn and scientists theorized that water could have been showering down into those bands from the rings. Then astronomers using ESA’s Infrared Observatory discovered the presence of trace amounts of water in Saturn’s atmosphere back in 1997, but couldn’t really find an explanation for why it was there and how it got there.

Then in 2011 observations with the Herschel space observatory determined water ice from geysers on Enceladus formed a giant ring of water vapor around Saturn.

But the bands seen by Voyager were not seen again until 2011 as well, when the team observed the planet with Keck Observatory’s NIRSPEC, a near-infrared spectrograph that combines broad wavelength coverage with high spectral resolution, allowing the observers to clearly see subtle emissions from the bright parts of Saturn.

The ring rain’s effect occurs in Saturn’s ionosphere (Earth has a similar ionosphere), where charged particles are produced when the otherwise neutral atmosphere is exposed to a flow of energetic particles or solar radiation. When the scientists tracked the pattern of emissions of a particular hydrogen molecule consisting of three hydrogen atoms (rather than the usual two), they expected to see a uniform planet-wide infrared glow.

What they observed instead was a series of light and dark bands with a pattern mimicking the planet’s rings. Saturn’s magnetic field “maps” the water-rich rings and the water-free gaps between rings onto the planet’s atmosphere.

They surmised that charged water particles from the planet’s rings were being drawn towards the planet by Saturn’s magnetic field and neutralizing the glowing triatomic hydrogen ions. This leaves large “shadows” in what would otherwise be a planet-wide infrared glow. These shadows cover 30 to 43 percent of the planet’s upper atmosphere surface from around 25 to 55 degrees latitude. This is a significantly larger area than suggested by the Voyager images.

Both Earth and Jupiter have a very uniformly glowing equatorial region. Scientists expected this pattern at Saturn, too, but they instead saw dramatic differences at different latitudes.

“Where Jupiter is glowing evenly across its equatorial regions, Saturn has dark bands where the water is falling in, darkening the ionosphere,” said Tom Stallard, one of the paper’s co-authors at Leicester. “We’re now also trying to investigate these features with an instrument on NASA’s Cassini spacecraft. If we’re successful, Cassini may allow us to view in more detail the way that water is removing ionized particles, such as any changes in the altitude or effects that come with the time of day.”

image: This artist’s concept illustrates how charged water particles flow into the Saturnian atmosphere from the planet’s rings, causing a reduction in atmospheric brightness. credit: NASA/JPL-Caltech/Space Science Institute/University of Leicester

invaderxan:

:(

(Source: robotshaming)

themagicofreality:

 Jupiter’s Great Red Spot in false color from Voyager 1979

(Source: thedemon-hauntedworld)

distant-traveller:

Colorful Saturn

This is an enhanced, false-color view of Saturn by the Voyager spacecraft.

Image credit: NASA/JPL

invaderxan:

Stardust

(Source: project-argus, via subatomiconsciousness)

The Purpose of the United States

Over the weekend I tweeted, somewhat provocatively, that the purpose of the British Empire was to enable Darwin to write and publish Origin of Species. Obviously this is a tongue-in-cheek statement, not meant to be taken entirely seriously. For one thing, it’s science-chauvinist, for it ignores all other kinds of accomplishments. Like many such statements, however, it has serious underpinnings. It addresses an important question, one that I believe all societies should ask of themselves on a regular basis. Boiled down, it can be stated as, “by what deed(s) will we be remembered?”

Twenty years ago, I might have argued that the United States would be remembered for the Apollo Program. Now, though, I have my doubts. Apollo now seems like a one-off, a fluke. It managed to do some magnificent science, though the Apollo scientific program was hardly comprehensive or even systematic. That we didn’t fly a lunar polar orbiter until the 1990s, for example, now seems bizarre, inexplicable. Everything about Apollo – for example, the restrictive Lunar-Orbit Rendezvous mode decision – was tailored to achieving its overriding geopolitical goal of an American on the moon ahead of the Russians and before the end of the 1960s. A comprehensive map of the geochemistry of the lunar surface just wasn’t necessary for that.

Now I argue that 1000 years from now playfully provocative science-chauvinists will say that the United States existed to accomplish the early reconnaissance exploration of our home, the Solar System. Depending on the kinds of exploration missions we decide to fly in the next few decades, they might drop the qualifier “early.” We need more orbiters, landers, and sample-return missions. We need to characterize the ice giants and more asteroids, visit some KBOs, dive into the Sun, and splash around in the oceans and lakes of the Outer Solar System.

I like to think that we might, for some reason that seems good at the time, get really, really ambitious, so that they’ll say that our purpose was to launch the first probe to another star. I like to imagine us launching an ultralight, relativistic “starwisp” probe by 2050 that reaches its goal – the five-planet system of Tau Ceti, anyone? – by 2101. Tau Ceti, a star four-fifths as massive as our own, is located a mere 11.9 light-years away. It’s the nearest single Sun-like star. Tau Ceti In This Century – now there’s a kick-ass slogan for you.

image: NASA

(Source: nasagifs)

explore-blog:

Happy Birthday, Pale Blue Dot – the iconic image of Earth seen from space, which inspired Carl Sagan, was taken on this day in 1990.

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stellar-indulgence:

1. Neptune Clouds
2. Neptune’s Great Dark Spot
3. Neptune Polar Projection
4. Neptune Voyager Image
5. Core of Neptune

Credit: [x]

Sagan & Swan’s Voyager Mars Landing Sites (1965)

Until the 1980s, most U.S. automated space explorers bore names connoting ventures into unknown parts – Explorer, Pioneer, Ranger, Surveyor, Mariner, and Voyager. Most people today identify the last of these names with the spectacularly successful pair of outer Solar System flyby spacecraft launched in the late 1970s. There was, however, an earlier Voyager program. First proposed in 1960 as a follow-on to the planned Mariner planetary flyby program, the original Voyager aimed to explore Venus and (especially) Mars using orbiters and landing capsules.

Carl Sagan, an assistant professor of astronomy at Harvard, and Paul Swan, Senior Project Scientist at Avco Corporation, published results of a study of possible Voyager Mars landing sites in the January-February 1965 issue of Journal of Spacecraft and Rockets. For their study, they invoked a Voyager design Avco had developed in 1963 on contract to NASA Headquarters. The “split-payload” design comprised an orbiter “bus” based on the Jet Propulsion Laboratory’s Mariner (or proposed advanced Mariner-B) design and a landing capsule shaped like the Apollo Command Module (that is, conical, with a bowl-shaped heat shield). Bus and capsule would leave Earth together on a Saturn IB rocket with an “S-VI” upper stage (a modified Centaur stage).

The Voyager lander would be sterilized to prevent biological contamination of Mars. Near Mars it would separate from the orbiter, enter the martian atmosphere, and float to a gentle touchdown suspended from a parachute. The Avco design included no landing rockets, which meant that more lander mass could be devoted to instruments for exploring the planet. The lander would operate on Mars for at least 180 days. The Voyager orbiter, meanwhile, would fire rockets to slow down so that Mars’s gravity could capture it into a polar orbit, from which it would image the entire martian surface and serve as a radio relay for the lander.

Swan and Sagan noted that operational constraints would limit possible Mars landing sites. For example, the orbiter and Earth would need to rise at least 10° above the horizon at the landing site to permit daily radio communication sessions, and the Sun would need to be rise at least 10° above the horizon so that the lander’s solar-powered science instruments could function properly. Such constraints would combine to create landing “footprints” that would vary widely depending on the Earth-Mars transfer opportunity used. The footprint for the 1969 minimum-energy opportunity, for example, would take the form of a north-pointing wedge centered on 270° longitude and spanning from 70° south to 60° north latitude.

Avco’s Voyager lander was designed so that it could be targeted to specific regions within such footprints, Sagan and Swan noted. They proposed that exobiologically interesting sites be accorded top priority in Voyager lander site selection. Sagan and Swan then looked at possible exobiologically interesting areas accessible to the Voyager landers launched during the 1969, 1971, 1973, and 1975 minimum-energy opportunities.

Their list of such sites was, of course, based entirely on Earth-based telescopic observations, for no spacecraft had yet visited Mars. They also used surface feature names that had been assigned by telescopic observers (image at top of post); those names would be superseded soon after the 1971-1972 Mariner 9 Mars orbiter mission.Sagan and Swan described the “wave of darkening” observed since the 19th century. The “wave” was regularly observed spreading from the pole to the equator in the martian springtime hemisphere. When they wrote their paper, it was widely interpreted as indicative of martian water, atmospheric circulation, and vegetation. Theory had it that, as the polar ice cap melted, atmospheric moisture increased and circulated toward the equator. Hardy plants then darkened as they absorbed the moisture from the thin air.

The first two Voyager landers would reach Mars on 31 October 1969, during springtime in the planet’s southern hemisphere. The wave of darkening would be near its peak, making it the best biological exploration opportunity until 1984. Top priority landing sites would include the northern hemisphere regions Solis Lacus and Syrtis Major, which Sagan and Swan described as the “[d]arkest of the Martian dark areas.” On the landing date, both regions would lie at the northern extreme of the southern hemisphere darkening wave and would be relatively warm.

Voyager spacecraft launched in the 1971 minimum-energy opportunity would arrive at the planet on 14 December 1971. Swan and Sagan noted that the 1971 opportunity would need the least amount of energy of any opportunity they considered, and suggested two possible ways of taking advantage of this. Four landers (two per orbiter) could reach Mars as the southern hemisphere wave of darkening faded. Top priority landing sites for this approach would be the southern polar cap, southern hemisphere dark areas Mare Cimmerium and Aurorae Sinus, and Lunae Palus in the north.

Alternately, the 1971 Voyager missions could use a higher-energy path to deliver two landers to Mars as the southern hemisphere darkening wave began. “Thus,” they wrote, “the exobiologically highly desirable characteristics of the 1969 arrival [could] be completely duplicated in the 1971 launch period.”

In the 1973 opportunity, which would see a landing on 24 February 1974, two landers would explore Mars’s deserts and “the so-called canal features.” The accessible landing sites would be relatively cold on the arrival date. Top-priority sites would include Propontis, a region containing a “typical Martian canal,” and Elysium, a “near circular anomalous bright region of ‘pinkish’ coloration” in the northern hemisphere.

Sagan and Swan proposed that two Voyager landers leave Earth during the 1975 minimum-energy opportunity. They would land on Mars on 28 August 1976. Top-priority sites would include the northern polar cap and Mare Cimmerium, where the wave of darkening would reach its peak as the 1975 landers arrived.

Swan and Sagan looked briefly at the possibility of launching Voyager spacecraft on the powerful Saturn V rockets that were under development for the Apollo manned lunar program at the time they wrote their paper. They found that “superior site selection could be performed” if the giant moon rocket were applied to Mars exploration. In fact, their “preliminary calculations” showed that “the landing footprints for all post-1971 opportunities may be made to superimpose on the [highly favorable] 1969 footprint” if the Saturn V were used.

The first successful automated Mars spacecraft, 261-kilogram Mariner IV, departed Cape Kennedy, Florida, on an Atlas-Agena rocket on 28 November 1964, and flew past Mars on 14-15 July 1965, six months after Sagan & Swan’s paper saw print. Mariner IV revealed a cratered, distressingly moon-like Mars with an atmosphere ten times less dense than expected. The 21 grainy images of the planet the little spacecraft beamed to Earth revealed no signs of water or life. The Avco Voyager design Sagan & Swan had invoked for their study would have depended entirely on parachutes to descend to a soft landing; Mariner IV showed that, while parachutes might still be used, heavy landing rockets would also be needed to enable a soft landing.

This new operational constraint contributed to NASA’s October 1965 decision to employ the Saturn V as Voyager’s launcher. At least as important as the new Mars atmosphere data in this decision was, however, the desire to find new tasks for the Saturn V after it had done its part to place a man on the moon. In 1964-1965, at the request of president Lyndon B. Johnson, NASA had begun to plan its post-Apollo future. In January 1965, the Future Programs Task Group, a body appointed by NASA Administrator James Webb, recommended that the post-Apollo NASA program be based on Apollo-Saturn hardware.Accordingly, in August 1965, NASA Headquarters formed the Saturn-Apollo Applications (SAA) Program Office. By mid-1966, SAA planners expected to fly as many as 40 manned missions using Saturn-Apollo hardware beginning in 1968.

At about the same time, NASA began high-level agency-wide studies of Saturn V-launched manned Mars/Venus flyby missions – what Charles Townes, chair of the President’s Science Advisory Committee, dubbed a “manned Voyager” program. The first of these missions was expected to leave Earth in 1975.

Despite Sagan & Swan’s endorsement of the Saturn V, the fledgling planetary science community harbored mixed feelings about the decision to launch Voyager spacecraft on the giant rocket. The decision in December 1965 to postpone the first Voyager mission to the 1973 Mars-Earth transfer opportunity reinforced these misgivings. Combined with the post-Mariner IV redesign, the switch to the Saturn V drove the estimated Voyager cost-per-mission past $2 billion. The high cost made the program increasingly vulnerable as NASA funding reached its Apollo-era peak in 1965-1966 and began a speedy decline.

In August 1967, in the wake of the Apollo 1 fire, Congress killed Voyager and manned flyby mission studies and slashed funding for the Apollo Applications Program (AAP), as SAA had become known. The manned flyby program all but disappeared from NASA’s collective memory and AAP shrank rapidly to become the Skylab Program. In October 1970, NASA permanently closed the Saturn V assembly line, which had been on standby since 1968. The last Saturn V to fly launched the Skylab Orbital Workshop in May 1973.

Voyager, for its part, rose again. In fact, one might argue that it rose again twice. In October 1967, NASA officials, citing Soviet planetary ambitions, met with Congressional leaders to propose a new NASA robotic program for the 1970s. In the new plan, which Congress first funded in 1968, Viking replaced Voyager. Like the Avco Voyager, Viking comprised a lander and a Mariner-derived orbiter; unlike Avco’s Voyager, the Viking orbiter was meant to retain its lander until after it had captured into Mars orbit. The Viking Program’s Titan IIIE-Centaur launch vehicle was approximately equivalent to Saturn IB-Centaur in capability.

Funding shortfalls pushed launch of the twin Vikings from 1973 to 1975. Viking 1 left Earth on 20 August 1975 (image at top of post), and Viking 2 followed on 9 September 1975. In July-August 1976, the Viking landers became the first and second spacecraft to land successfully on Mars.

Meanwhile, in 1972, Congress approved the Mariner Jupiter-Saturn (MJS) flyby mission. The twin MJS spacecraft were christened Voyager 1 and Voyager 2 and launched in 1977. Voyager 1 flew past Jupiter (1979) and Saturn (1980); Voyager 2 flew past Jupiter (1979), Saturn (1981), Uranus (1986), and Neptune (1989). To date, Voyager 2 remains the only spacecraft from Earth to have visited Uranus and Neptune.

Carl Sagan’s career after 1965 is well documented. He was involved in nearly all subsequent planetary missions, including the twin Vikings and twin Voyagers, and became by the early 1980s arguably the most important science popularizer since Galileo Galilei. His death at age 62 in December 1996 left a void that has not been filled. Paul Swan, for his part, led Avco’s seminal 1966 study of manned Mars surface operations and joined the staff of NASA’s Ames Research Center by 1970. He remained active there until at least the late 1970s.

The Voyagers continue to operate more than 34 years after launch and more than 50 years after the Voyager name was first proposed. Voyager 1 is the most distant human-made object; at this writing it is about 120 Astronomical Units (AUs) out (one AU = the Earth-Sun distance of about 93 million miles). Sunlight needs more than 17 hours to reach Voyager 1. Both Voyagers have entered a poorly understood borderland called the heliosheath; Voyager 1 is widely expected to cross the heliopause and enter interstellar space before 2015.

image 2: Avco’s 1963 Voyager design. Image: NASA
image 3: The U.S. Air Force Aeronautical Chart and Information Center based its MEC-1 prototype Mars map on data current as of 1962. This is the Mars Sagan & Swan knew when they planned their Voyager landing sites. Image: U.S. Air Force/Lunar and Planetary Institute
image 4: Mariner IV captured image frame 11E at a distance of 12,600 kilometers from Mars on 15 July 1965. The largest crater in the frame, which is 151 kilometers wide, was named Mariner in honor of the spacecraft. The frame is centered in the region labeled Mare Cimmerium in the MEC-1 map above. Image: NASA
image 5: Voyager as envisioned shortly before its cancellation in 1967. Two such spacecraft would have been launched on a single Saturn V rocket. Image: NASA
image 6: The twin Voyagers are outward bound for the stars. Image: NASA

Reference:
Martian Landing Sites for the Voyager Mission, P. Swan and C. Sagan, Journal of Spacecraft and Rockets, Volume 2, Number 1, January-February 1965, pp. 18-25.

pennyfournasa:

“Voyager cost each American less than a penny a year from launch to Neptune encounter.” - Carl Sagan, Pale Blue Dot

Tell Congress To Spare A Penny4NASA:
http://www.penny4nasa.org/take-action/

sciencesoup:

The Grand Tour Continues

Over the past 35 years the Voyager probes have been an inspiration to many, a human project spanning the generations. Originally envisioned as a grand tour of the planets, the mission expanded to encompass the outer reaches of the solar system and beyond into interstellar space. A rare planetary alignment facilitated the use of the gravity assist technique. This dance among the planets allowed the probes to steal kinetic energy, accelerating to extraordinary speeds; they will travel a further 1000 km in the time it takes you to read this article. The venerable spacecraft continue to provide new revelations, such as the discovery in 2011 of ‘magnetic bubbles’ in the heliosheath separating the Sun’s sphere of influence from the interstellar medium. It now appears that in the wrinkled and twisted fringe of the Sun’s magnetic field, magnetic reconnection forms self-contained regions more than 100 million km across, with only tenuous connections to the broad structure of the solar magnetic field. A ‘foam’ of magnetic bubbles may even form a partial barrier, protecting the solar system from bombardment by cosmic rays. It is a testament to the robustness of the 1970s era technology that most instruments are still available for use, although many have been disabled to conserve energy. The onboard radioisotope thermoelectric generators are projected to keep some instruments functioning until 2025. What then? In 40,000 years, Voyager 1 will pass within 1.6 light years of the star Gliese 445. With no power and hence no electromagnetic emissions, it seems a forlorn hope that this tiny spec in a vast cosmos will ever be discovered by another civilisation. But just in case, both probes carry with them the Voyager Golden Record, bearing messages from J.S. Bach, Chuck Berry and others, painting a picture of humanity for whomever they might encounter.

Guest article by Jeffrey Philippson