NASA's Juno Spacecraft Headed to Jupiter Friday

Mission may solve mysteries of planet birth, astronomers say.

An artist's rendering shows the Juno spacecraft in orbit above Jupiter.

Illustration courtesy NASA/Caltech

Brian Handwerk

for National Geographic News

Published August 4, 2011

This Friday a NASA spacecraft is slated to launch on a five-year journey toJupiter.

When it arrives, the craft will probe deeper into the gas giant planet than any previous mission, searching for the unseen core hidden below the thick atmosphere. It will also endure the solar system's strongest radiation zone to study the origins of the giant auroras that dance across Jupiter's poles.

The probe—dubbed Juno—will blast off from Florida aboard an Atlas V rocket, starting a 400-million-mile (644-million-kilometer) trek.

When it arrives at Jupiter in 2016, the spacecraft will spend about one Earth year making 33 elliptical polar orbits, skimming as close as 3,100 miles (5,000 kilometers) above the clouds.

Watch NASA video about the Juno mission.

Carrying a suite of eight main science instruments, Juno will collect data on Jupiter's atmosphere that may be key to understanding the birth of our cosmic neighborhood. (Also see "New Model of Jupiter's Core Ignites Planet Birth Debate.")

"We're really trying to understand the origins of Jupiter—how it formed, the role it played in the formation of the rest of our solar system, and what that can tell us about the solar systems that we're discovering around other stars now," said Juno's principal investigator, Scott Bolton, of the Southwest Research Institute (SwRI) in Colorado.

By delving far beneath the colorful zones and belts of Jupiter's high clouds, the Juno mission also aims to answer some fundamental questions about the planet's mysterious inner workings.

"It's as exciting as learning about the deep ocean," said Timothy Dowling, a planetary-atmosphere expert at the University of Louisville in Kentucky who's not part of the Juno team.

"It has that same feel. All that we see on Jupiter—the light and dark bands, the jets, the enormous storms—we'll explore the foundation underneath all of that."

(Related: "Jupiter Loses Big Belt; Great Spot Left Hanging.")

Jupiter Water May Offer Clues to Planet Birth

Jupiter may already seem well studied, since spacecraft headed elsewhere in the solar system have taken countless pictures as they swung close to the planet to use its gravity like a slingshot. (Related: "Lightning Strikes, Changing Climate Revealed on Jupiter.")

But until now only one other probe, Galileo, has orbited the giant world and attempted to study its composition and activity.

As the largest planet in our solar system, Jupiter could help resolve theories for the process of planet formation.

Current theory states that the planets formed from a dusty disk of material that surrounded the newborn sun roughly 4.6 billion years ago. (Related: "Newborn Planet Found Orbiting Young Star.")

Scientists know that Jupiter is primarily made of hydrogen and helium, like the sun and most of the universe. But the planet is also enriched with heavier elements such as carbon and nitrogen—elements that became the building blocks for not only the rocky planets such as Earth and Mars but also for life.

One theory to explain the heavy elements in Jupiter is that water, in the form of ice, was one of the first multielement molecules to form inside the protoplanetary disk.

This ice clumped together and trapped heavy elements in the dust to make dirty snowballs called planetesimals. In Jupiter's case, an ice ball may have attracted gases as it swept through the disk, building up the planet's mass.

Juno will help test that theory using a device called a passive microwave radiometer, which will measure how much water is in Jupiter's deep atmosphere. In this region, gravity is so intense that much of the primordial solar material that formed the planets is probably still trapped.

"I think it's a very fundamental mission, in the sense that we're tying to go back and look at the first step in the solar system's history after the sun formed and investigate why the planets are the way they are," SwRI's Bolton said.

Juno Probing Jupiter's Depths

Other instruments on Juno will map the circulation, composition, temperature, and other features deeper in Jupiter's atmosphere than any previous experiments.

"Essentially we'll be unraveling basic aspects of how meteorology works in an alien environment, thereby extending our understanding of atmospheric circulation and climate beyond the confines of Earth," said Adam Showman, of the University of Arizona's Lunar and Planetary Laboratory.

"I think that's pretty exciting, especially because gas giants like Jupiter are among the most common planetary environments in the universe."

(Related: "New Planet Found; Star's Fourth World Stumps Astronomers.")

And while Jupiter is nearly all atmosphere, the planet should have some kind of solid core far beneath the swirling clouds, where atmospheric pressures are millions of times greater than at sea level on Earth.

By precisely measuring the way Juno gets pulled and pushed by the massive planet's gravity field, scientists may finally be able to detect and measure the planet's core.

"This mission is very unique," said the University of Louisville's Dowling. "We've never tried to probe into the heart of a planet like Jupiter. It's basically the first time we'll see an MRI of a gas giant."

Juno Needs "Radiation Vault" to Survive

In addition to peering far below Jupiter's surface, Juno will be gazing high above the clouds, studying the origins of the planet's intense magnetic field and how it interacts with the Jovian atmosphere.

The biggest and strongest magnetic dynamo in the solar system, Jupiter's magnetic field creates spectacular "hyperauroras," which Juno will see in unprecedented detail.

(See "Jupiter Auroras Fed by Largest Moon's Magnetic 'Bubble.'")

Juno will also sample the charged particles that create the auroras and will observe them in ultraviolet light. In addition, the spacecraft will capture color photos of the poles with its JunoCam—sure to be one of the mission's most popular features.

"That camera is really for the public, and the data will be immediately made available for the public—but I want to see a picture of the poles too," SwRI's Bolton said.

But the magnetic field that drives Jupiter's auroras also traps charged particles in a bubble around the planet, creating the strongest radiation zone in the solar system, something that would fricassee the spacecraft without special precautions.

"We basically have a radiation vault—a titanium box in the middle of the spacecraft—and the sensitive electronics are inside that box, like an armored tank going to Jupiter," Bolton said.

At Mission's End, Juno to Plunge Into Jupiter

In the end, Jupiter's radiation will degrade the solar cells on Juno's arrays, putting limits on the lifetime of the mission.

Unlike previous deep-space missions, which used nuclear power, Juno will operate entirely on sunlight. When it reaches Jupiter, it will be the most distant solar-powered spacecraft yet launched.

The craft's three superefficient arrays—each 9 by 30 feet (2.7 by 9.1 meters)—will allow it to work in sunlight that's about 25 times weaker than the light here on Earth.

When Juno's mission ends, NASA scientists will instruct the craft to deorbit over Jupiter so that Juno burns up in the giant planet's atmosphere. This way, the defunct spacecraft won't be left to wander the Jovian system and potentially crash on one of the planet's many moons, contaminating worlds such as Europa with watery habitats that possibly host life.

Ultimately, the Juno mission will provide scientists with a wealth of data for understanding not just our own solar system but also the scores of gas giants scattered across the galaxy.

"Jupiter is our prototype giant planet," the University of Arizona's Showman said. "So the understanding we gain from Juno about Jupiter will lend great insights to our understanding of the hundreds of giant planets being discovered around other stars."

Earth Had Two Moons, New Model Suggests

                  Slow collision between lunar companions could solve moon mystery.

The near side of the moon (right) is much smoother than the far side.

Photograph courtesy NASA

Ker Than

for National Geographic News

Published August 3, 2011

Earth may have once had two moons, but one was destroyed in a slow-motion collision that left our current lunar orb lumpier on one side than the other, scientists say.

Astronomers have long been puzzled by the differences between the side of the moon that always faces Earth—the near side—and the side that always faces away, the far side. The topography of the near side is relatively low and flat, while that of the far side is high and mountainous with a much thicker crust.

(Take a moon mysteries and myths quiz.)

According to a new computer model, this discrepancy can be explained if a smaller "companion moon" collided with our moon's far side early in its history. Such a collision would have left the far side splattered with especially hard rocky material that now forms the current lunar highlands.

For the theory to work, the smaller moon must have crashed into the larger one at about 4,400 miles (7,081 kilometers) an hour.

"This is the slowest possible collision the two massive bodies could have if they fell into each other’s gravity," explained study co-author Erik Asphaug, a planetary scientist at the University of California, Santa Cruz (UCSC).

At this relatively slow speed, the far-side collision wouldn’t have been energetic enough to melt rock or carve out a crater. But it would have been forceful enough to plaster material from the smaller moon onto the larger moon.

"It's like a car crash, where you have crumpled bumpers but you don't melt the cars as they're colliding," Asphaug said. "This is the same kind of phenomenon."

Moon Collision Created Meteor Shower

The new theory, by Asphaug and UCSC postdoctoral researcher Martin Jutzi, is detailed in the current issue of the journal Nature.

According to their model, the two moons coexisted peacefully for about 80 million years, each in its own stable orbit. The moons were the same color and composition, but one was about three times larger than the other, Asphaug said.

"Our moon looked like a big dinner plate in the sky ... and when it set, there was this other moon trailing it by about 60 degrees," he said.

(Related: "Trojan Asteroid Found Sharing Earth's Orbit—A First.")

This brief period of lunar harmony was shattered, according to the model, when natural gravitational interactions with Earth caused both moons to drift farther away from our planet. The sun's gravitational tug then destabilized the smaller moon’s orbit and caused it to fall into its larger sibling.

Though not very energetic, the collision would have ejected trillions of tons of lunar debris into space, obscuring both moons for several days.

"When the dust cleared, you had one moon that might have looked similar to our moon today," Asphaug said.

For up to a million years after the event, Earth would have been bombarded by moon bits of various sizes, the biggest of which could have been as much as 62 miles (100 kilometers) across.

"You'd have meteors raining down all over the sky for a long period of time," Asphaug said, though there probably would have been no life yet on Earth to witness the spectacular sky shows.

Lunar Smashup Opens Up "Cool Problems"

Astronomer Jeffrey Taylor of the University of Hawaii said the new moon theory is very interesting and worth further investigation.

Asphaug and Jutzi's model not only accounts for the moon's asymmetry, Taylor said, but the findings also explain the fates of the smaller, companion satellites that another theory predicts should have formed alongside our moon.

One of the leading theories for how our moon formed is that it was born after a Mars-size planet crashed into Earth shortly after the solar system's formation about 4.5 billion years ago. (See "Earth-Asteroid Collision Formed Moon Later Than Thought.")

Scientists think the earlier smashup created a ring of molten rock debris around Earth, which eventually coalesced into several bodies, including our current moon. (Related: "The Moon Has Shrunk, and May Still Be Contracting.")

But "if that's the case, what happened [to the smaller moons]? This is one thing that could have happened to them," said Taylor, who was not involved in the study.

The new theory isn't without its problems, however. For example, it doesn't explain why the lumpy far side of our moon shows a high concentration of aluminum, Taylor said.

If the two moons had formed from the same material, as is assumed, the companion moon—and its splatterings—should have been low in aluminum, like our own moon's interior.

(Related: "Ancient Moon Had Earthlike Core?")

However, this problem could be resolved by future lunar studies, Taylor said, and it's not a serious enough reason to dismiss the theory.

"If anything," he said, "it just opens up more cool problems to work on.

Space exploration and the shuttle: our eyes are still on the final frontier

If I had to pinpoint the event that launched me on a career in science, it was watching those grainy black-and-white images of Neil Armstrong's historic first step on the powdery lunar surface.

Nasa, the American space agency, has come a long way since the Eagle landed in July 1969. It has given us feats of breathtaking bravery; the most remarkable rescue in history, when the crew of Apollo 13 was returned safely to Earth; jaw-dropping insights into every major object in the solar system; and even the first interstellar mission. Two nuclear-powered Voyager probes, launched in 1977, remain on course to reach distances well over 10 billion miles from the Sun within the coming decade.

This week, there has been much agonising over the future of Nasa, prompted by the final flight of the Space Shuttle programme. The mission marks the end of three decades in which the Shuttle never managed to rekindle the excitement of the great Apollo adventure – or, as promised, to make spaceflight cheap and routine. It also saw two catastrophes – the losses of Columbia and Challenger, along with 14 astronauts – that shattered public confidence in Nasa.

Many today believe that the agency has lost its way. It has cancelled its Ares launcher programme – which would have provided the boost to take humans back to the Moon, and on to Mars – and is about to convert its Shuttles into museum pieces without a clear idea of what comes next. After this mission, America will be dependent on its former rival, using Russia's Soyuz and Progress vehicles to supply the International Space Station. Neil Armstrong, along with other astronauts, has expressed his alarm that Nasa has ignored a golden rule of space exploration: always have a back-up plan.

Nasa's budget has fallen victim to wrangling between Congress and the Obama administration. The House just released its appropriations Bill, which gives Nasa funding of $16.8 billion, $1.6 billion below last year's level and $1.9 billion below the president's request. It has also axed the James Webb Space Telescope, Hubble's successor, to the consternation of scientists.

As for where Nasa goes next, the president has given only a vague outline, in the form of missions to an asteroid and Mars. From the perspective of any space cadet from 1969, this isn't very impressive. Moments before Armstrong's Apollo 11 booster lifted off from Cape Kennedy, vice-president Spiro Agnew declared that the next goal should be a manned landing on Mars by the end of the century. A presidential committee on post-Apollo objectives – which Agnew happened to head – predicted that America could send astronauts to Mars by the mid-Eighties for not much more than the $24 billion cost of Apollo. No wonder Armstrong has criticised Obama's plans.

Nasa's administrator, Charles Bolden, insists that his agency has a future and has promised to maintain American leadership in space travel for the next half-century. He wants to leave low-Earth-orbit missions to the private sector, so that Nasa can focus on deep space exploration.

In part, this is an acknowledgement of how much has changed since the Cold War spurred Kennedy to declare that he wanted to reach the Moon. Private space ventures have taken off. There is Richard Branson's Virgin Galactic, which will use a spaceplane strapped to a mothership to reach the edge of space. Meanwhile, Armadillo Aerospace in Texas is developing vertical takeoff, vertical landing spacecraft.

Then there's SpaceX of Hawthorne, California, led by the internet entrepreneur Elon Musk, which has tested the Falcon 9 rocket and Dragon space capsule, which the company hopes to use to run a taxi service to the International Space Station. Boeing is working on a crew capsule of its own, called the CST-100. The Las Vegas company Bigelow Aerospace plans to create orbiting hotels in inflatable space stations. And why stop at missions around our home planet? Musk is even talking to getting to Mars in a decade or two.

The nature of the space race has also changed profoundly since 1969. In all, nine countries have placed payloads in orbit. Citizens of almost 40 countries have now flown into space. Meanwhile, India and China have announced ambitious plans.

There's no doubt the current economic situation is going to hold back space exploration for a while. But I, for one, have no doubt that over the next half-century, space will maintain its ability to grip the human imagination as only the final frontier can. Is the dream over? Far from it. Be prepared for the next giant leap.

Roger Highfield is the editor of 'New Scientist'

Weather May Play Spoilsport Ahead of Atlantis’ Launch

On July 8th, 2011, Space shuttle Atlantis is scheduled to embark on what is going to be the last in NASA’s glorious 30-year space shuttle program history. Carrying a team of four astronauts, and a supply package, along with spare parts to the International Space Station, Atlantis is scheduled to launch from Launch Pad 39A, Kennedy Space Center in Cape Canaveral.

Shrouded in uncertainty...

However, on the eve of the NASA’s final shuttle, according to a report on Space.com, worries of the weather not being compliant, may lead to scrapping of the scheduled launch, and setting it to another day. But, the officials are optimistic and believe that all they need to make that perfect launch is that one hole in the cloud. And, quoting Launch Director, Mike Leinbach who disregards delays, “We want to play the game Friday.” So, a Friday is all that we wait for.

Astronauts Leave Cameras Behind in Space

While most of us would do almost anything for a good high-end DSLR, NASA astronauts are used to leaving behind camera equipment in space. The last Endeavor crew and specifically, Italian astronaut Paolo Nespoli carried some camera equipment up to space to shoot photographs. He was carrying a Nikon D3s and a D2Xs full-frame sensor camera with a 24-120mm lens. The value of the equipment taken to space was roughly $8,000. The D3x isn't exactly a cheap camera. After clicking several photos in the ISS, he returned back to earth in a Soyuz spacecraft. But before he did that, he dumped the cameras into a capsule that detaches itself from the spacecraft before re-entry. The constituents of the capsule are all disintegrated during re-entry. The memory cards were carried with the astronauts on their way back to earth. There’s a cargo checking process that is done by Russian authorities before the astronaut can take the memory cards back with him. Paolo Nespoli is said to have clicked photos from a distance of 200m from the international space station. He was also said to be carrying a Fujifilm FinePix 3D W1 camera with him.

Black Hole Caught Eating a Star, Gamma-Ray Flash Hints

A huge "belch" of radiation from a supermassive black hole indicates that the cosmic monster recently devoured a star, scientists say.
Earlier this year astronomers spied a burst of high-energy gamma rays emanating from the center of a dwarf galaxy 3.8 billion light-years away. The odd flash, dubbed Sw 1644+57, is one is the brightest and longest gamma ray bursts (GRBs) yet seen.
In visible light and infrared wavelengths, the burst is as bright as a hundred billion suns.
"We believe this explosive event was caused by a supermassive black hole ten million times the mass of the sun shredding a star that got too close to its gravitational pull," said study leader Joshua Bloom, an astronomer at the University of California, Berkeley.
"The mass of the star fell into the black hole, but along the way it heated up and produced a burst of energy in the form of a powerful jet of radiation, [which] we were able to detect through space-based observatories."

While supermassive black holes are thought to be lurking at the hearts of most large galaxies, events such as a star getting eaten may happen only once every hundred million years in any given galaxy.
"What makes this event even more rare is that we didn't just get a burst of x-ray emissions from the infalling stellar gas, but some of it actually got spit out by the black hole in the form of a gamma ray jet, and we just happen to be looking down the barrel of that jet," Bloom said.
"So I would say it's a combination of actually catching a monster black hole in the process of feeding on an unfortunate star that got too close to it, and because we are in a fairly special geometry."
Star's Death Caused Uncommon Flare
NASA's Swift satellite first detected the burst on March 28, 2011, and both the Hubble Space Telescope and the Chandra X-ray Observatory followed the burst's progress.
The explosive event was initially thought to be an ordinary gamma ray burst. Originating billions of light-years away, these events are seen every few days across the universe, and they're thought to occur when very massive stars blow up or when two giant stars collide.
"Most of these [common gamma ray bursts] are detected and quickly fade away within the course of a day," Bloom said.

"But now after two and half months, this new GRB is still going strong. Because it stands out so much observationally, this decidedly makes it something different from any other GRB we have ever seen before."
In addition, common gamma ray bursts are normally spied off-center in the main bodies of galaxies. But Sw 1644+57 was found in an unusual location—at the core of a galaxy.
"That's the prime reason we started suspecting early on that a supermassive black hole was involved, because we know [galactic cores are] where these beasts reside."
Scientists already knew that actively feeding galactic black holes emit huge amounts of radiation, because material falling in gets superheated as it nears the black hole's maw. Sw 1644+57 is surprising, though, because of its spontaneous nature.
"What's amazing," Bloom said, "is that we have here an otherwise quiescent, starving black hole that has decided to go on a sudden feeding frenzy for a short period of time."
Our own Milky Way also has a quiet supermassive black hole at its center. The new discovery shows it's possible for our cosmic monster to spew powerful radiation jets should a star fall in, Bloom added.
Still, because such events are so rare—and the resulting jets are so narrowly focused—it's unlikely we'd detect anything like Sw 1644+57 shooting from our galaxy for millions of years.
The black hole eating a star is described in this week's issue of the journal Science.

Earth Farthest From Sun on Fourth of July -- Why So Hot

The sun sets over Los Alamos National Laboratory in New Mexico on Wednesday.

Photograph by Eric Draper, Reuters

If the sun looks a little smaller than usual as you're barbecuing this Fourth of July, it's not your imagination: Earth will be farther from the sun on Monday than on any other day this year.
That's because the orbits of all the planets in our solar system—including Earth's—are not perfectly circular, a phenomenon that was first explained in mathematical detail by the 17th-century German astronomer Johannes Kepler.
Kepler "figured out the orbits of the planets were elliptical in shape and that the sun was offset from the center," explained Mark Hammergren, an astronomer at the Adler Planetarium in Chicago, Illinois.
Earth's elliptical orbit means there will be a point each year when the planet is closest to the sun, called perihelion, and a point when it is farthest away, known as aphelion.


On July 4 our planet will be at aphelion—94,511,923 miles (152,102,196 kilometers) from the sun. This year's perihelion was on January 3, when Earth was 92,955,807 miles (149,597,870 kilometers) from the sun.
On average, Earth is about three million miles—or about 3 percent—farther from the sun at aphelion than at perihelion.
As a result, the apparent size of the sun in the sky will be about 3 percent smaller, but you may not notice the difference without a telescope.
"It's probably not noticeable, but it's certainly measurable," Hammergren said.


Distance Won't Dampen Fourth of July Heat
So if Earth is at its maximum distance from the sun on the Fourth of July, why are those of us in the Northern Hemisphere sweltering in the heat of summer?
Because it's the tilt of the Earth and not our distance from the sun that determines the seasons, Hammergren said.
Earth's north-south axis is tilted by about 23.4 degrees, so during its orbit, the poles point in different directions from the sun.
By coincidence, Earth reaches aphelion when the North Pole is tilted more toward the sun than the South Pole.
"Because the Earth has a tilt, it means that in the summer months [the Northern Hemisphere] receives a longer duration of sunshine—so the day is longer and the night is shorter—but also the sunlight hits the ground more vertically," Hammergren said.
"Those two things together contribute to the difference in heating for the seasons."

Space Pictures This Week: Lunar Sunrise, Saturn Slice, More

Distant, but Bright 

Lunar Sunrise

Eritrea Eruption

Starry Spectacle

A Cut Above

Only penguins can see solar eclipse

A peculiar partial solar eclipse will take place on Friday. It will, however, not be visible anywhere in the world except the Antarctica, where it is likely to be seen only by penguins and sea birds. Partial solar eclipses taking place over the polar region, such as this one over the Antarctica, are peculiar in the sense that the centre of the shadow of the moon just misses the earth, Arvind Paranjpye of Inter-University Centre for Astronomy and Astrophysics said.

The partial solar eclipse will begin at 1.23 p.m. Indian Standard Time and will end at 2.53 p.m. It will reach its maximum at 2.09 p.m. IST.

The total duration of the celestial phenomenon will be for about an hour and a half.

The partial solar eclipse will be visible from southern latitudes and the Antarctica, Science Popularisation Association of Communicators and Educators (SPACE) president C.B. Devgun told PTI.

This southern hemisphere event is visible from a D-shaped region in the Antarctic Ocean, to the south of Africa, Mr. Paranjpye said.

Russian Soyuz docks at ISS

A Russian Soyuz capsule docked Thursday at the International Space Station, bringing new Russian, U.S. and Japanese crew members to orbiting outpost 350 kilometres above the Earth.

The TMA-02M capsule, which was outfitted with new digital controls, blasted off from the Baikonur cosmodrome in Kazakhstan at 2:12 am (2012 GMT Tuesday), the Russian space agency Roscosmos said.

Cosmonaut Sergey Volkov and astronauts Satoshi Furukawa and Michael Fossum will remain at the ISS until November 16.

Their mission will see the last visit by a U.S. space shuttle to the ISS when the Atlantis launches in July. After the shuttle fleet is retired, U.S. astronauts will have to rely on the Soyuz for transportation to the ISS.

The new crew members are joining Russians Andrey Borisenko and Alexander Samokutyaev and American Ron Garan.