Thousands of Worlds Could Lurk Beyond Pluto – This New Animation Shows Them AlI


Welcome to our cosmic neighbourhood.

 You may be familiar with our Solar System’s eight planets – Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. There’s also their famous dwarf-planet companion, Pluto.

But this icy world may just be an appetiser to what lurks beyond in a region called the Kuiper Belt.

 

As this stunning animation suggests, dwarf planets may outnumber regular planets 100- or even 1,000-fold.

However, if a small group of astronomers gets its way, most of these worlds may become fully fledged planets and drop the “dwarf” label.

Where the animation comes from

We first saw the animation in a Reddit post by user Nobilitie. It’s actually a recording of a physics-based simulator game called Universe Sandbox2, according to Dan Dixon, the creator and director of the software.

Each ring represents an object’s orbit, and the mess of rings beyond the inner eight rings all belong to dwarf planets.

In response to the Reddit post, Dixon said the orbits are based on a constantly updated list of candidate worlds maintained by Mike Brown, an astronomer at Caltech.

 “[I]t’s a nice illustration of what is out there!” Brown wrote in an email to Business Insider. “The striking difference between the orderly giant planets and the randomness of the dwarf planets is quite apparent.”

Brown is the person who discovered Eris, a 10th solar system object that’s about 27 percent more massive than Pluto.

artist impression of the dwarf planet Eris

Artist impression of Eris, ESO/L. Calçada and Nick Risinger

His find eventually ‘killed‘ Pluto as a bonafide planet in 2006. That’s when thousands of astronomers voted on new celestial terminology, categorising the world as a “dwarf planet” alongside Eris.

Some astronomers disagreed with the decision, with one going so far as to call it “bullsh-t”. The public also didn’t take it well: Brown has since received a torrent of hate mail from schoolchildren.

Definitions aside, the list kept by Brown sorts objects detected in deep space based on the likelihood of their existence. Larger, inner objects tend to be more certain while farther-out objects are less certain.

Pluto, Eris, Ceres, Makemake, Haumea, and five others meet Brown’s “near certainty” criteria – in other words, they’re definitely dwarf planets and not comets or some other astronomical object. Thirty are “highly likely” to be dwarf planets, 75 are “likely,” and nearly 850 other objects are “probably” or “possibly” dwarf planets.

Brown guessed that about half of the dwarf planet candidates have yet to be detected, bringing their numbers close to 2,000 or more.

Redefining “planet” again?

Pluto's orbit and Kuiper's belt objects

Even Brown’s best estimate may be low, though. In the illustration above, Pluto’s orbit is shown in yellow, and the dots beyond it are Kuiper Belt objects.

“[A]s you can see from the illustration, some of them are on exceedingly elliptical orbits. Those guys are going to spend most of their time at the outer edge of their orbit, so they’re hard to see,” Brown said. “There might be a factor of ~5 more of those objects that we don’t know about!”

Brown doesn’t think nuclear-powered spacecraft like New Horizons, which can last for decades and is now exploring the Kuiper Belt, will discover most of those missing worlds.

“The fact that there are so many of these things out there really shows that the future of their exploration is going to mostly rely on telescopes,” he said.

A twist in all of this is that astronomers are once again wondering what to call floating orbs of rock, metal, and ice in space, according to a poster that seven researchers are presenting this week at the 48th Lunar & Planetary Science Conference.

Instead of categorising worlds as planets, dwarf planets, and moons – terms based on their orbits around the sun and one other – the team wants to simplify the system: As long as an object is big enough to be mostly round and isn’t fusing hot gases (like the Sun), it should be deemed a planet.

If enough astronomers agree with them, the solar system might suddenly contain 110 official planets – and perhaps hundreds or even thousands more if Brown’s list pans out.

Nasa’s Juno probe to make closest pass of Jupiter.


Scientists expect unprecedented images of gas giant as $1.1bn probe makes first pass using full set of instruments and cameras.

 An artist’s impression of the Juno spacecraft approaching Jupiter.Nasa’s Juno spacecraft will make its closest pass of Jupiter on Saturday when it soars over the swirling cloud tops of the solar system’s largest planet at more than 125,000 miles per hour.

The close encounter will be the first time the $1.1bn (£840m) probe has its full suite of cameras and scientific instruments switched on and turned towards the planet as it flies overhead at an altitude of 2,600 miles.

Mission scientists expect the spacecraft to capture the most spectacular images of the planet yet and reveal in unprecedented detail what lies beneath Jupiter’s thick blanket of cloud.

The flyby at 1.51pm BST will be the first opportunity for Juno to get so close to the gas giant since the probe arrived in orbit on 4 July. When the spacecraft reached Jupiter, all of its scientific instruments were shut down to ensure nothing interfered with the crucial braking manoeuvre needed to stop Juno from barrelling past the planet.

The spacecraft is now on a highly elliptical orbit that takes it far away from Jupiter’s dangerous radiation belts before swinging back in and passing close over the north and south poles that flicker with brilliant aurorae more than 1,000 times brighter than those on Earth.

“We are very excited, and really just anxious to see what the poles of Jupiter will look like. No other spacecraft has gotten a good look at them before,” said Candice Hansen, a co-investigator on the Juno mission at the Planetary Science Institute in Tucson, Arizona.

The spacecraft will shoot across the Jovian sky with eight scientific instruments switched on and the probe’s main camera, JunoCam, ready to take snapshots of the atmosphere and poles. The first images from the flyby are expected to be released towards the end of next week. Scientific data from the encounter will take longer to be processed and analysed.

“They will be using JunoCam to take some really high-resolution images of the atmosphere, which promise to be delectable,” said Tom Stallard, an astronomer at Leicester University, home to the UK’s only research team associated with the Juno mission. “We’re all very positive. This is a mission Nasa has planned for a very long time, so this is the fruition of a lot of work.”

The radiation belts that wrap around Jupiter are so intense that Juno’s most essential electronics are encased in a titanium vault. The probe’s sensors and instruments are harder to protect and will take a battering from the hostile rays with every pass around the planet.

“We’ll have some amazing orbits and collect some great data, and then as time goes by it will get more and more difficult, but Jupiter is difficult,” said Stallard.

The spacecraft will perform 35 more flybys during its primary mission, which is due to end in February 2018 when mission controllers command the probe to plunge into the Jovian clouds, never to be seen again.

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Io has a unique collapsing atmosphere.


Jupiter’s closest moon, Io, has an atmosphere that collapses when it is eclipsed by the gas giant.
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An artist’s interpretation of Io’s collapsing atmosphere when in Jupiter’s shadow

As one of the four Galilean moons, Io has played an important role in Astronomy since its discovery in 1610. It is the fourth largest moon in the solar system while also being the most geologically active, but a new study may add a new and interesting aspect to this moon.

Using the the Gemini North telescope and its instrument the Texas Echelon Cross Echelle Spectrograph (TEXES), a group of scientists documented unique atmospheric changes on Io. They found that Io’s thin atmosphere, which is mostly sulfur dioxide gas vented from volcanoes, collapses and freezes onto the surface when shaded by Jupiter. The results are published in the Journal of Geophysical Research-Planets.

“This research is the first time scientists have observed this phenomenon directly, improving our understanding of this geologically active moon,” says Constantine Tsang, lead author and senior research scientist at Southwest Research Institute’s (SwRI) Space Science and Engineering Division, in a press release.

Once temperatures on the moon drop below -235 degrees Fahrenheit during an eclipse, Io’s atmosphere appears to “deflate.” These eclipses occur fairly frequently; two hours of every Io “year” (it orbits Jupiter once every 1.7 Earth days) it is eclipsed. Most of the sulfur dioxide gas in the atmosphere settles to the moon’s surface as frost during a full eclipse. Once the moon warms from sunlight, the atmosphere redevelops.

“This confirms that Io’s atmosphere is in a constant state of collapse and repair, and shows that a large fraction of the atmosphere is supported by sublimation of sulfur dioxide ice,” says John Spencer, a SwRI scientist who also participated in the study. “Though Io’s hyperactive volcanoes are the ultimate source of the sulfur dioxide, sunlight controls the atmospheric pressure on a daily basis by controlling the temperature of the ice on the surface. We’ve long suspected this, but can finally watch it happen.”

This is the first time there have been direct observations of Io’s atmosphere in eclipse as it is very difficult to observe the atmosphere in the darkness of Jupiter’s shadow. Thanks to the specific capabilities of the TEXES instrument, this breakthrough was possible. The instrument measures the heat radiation emanating from the atmosphere not the sunlight, therefore Gemini was able to pick up the faint heat signatures of Io’s collapsing atmosphere.

 

The observations occurred over a two night stretch back in November of 2013 when Io was more than 675 million kilometers (420 million miles) from the Earth. Io was observed while moving in and out of Jupiter’s shadow for a period of about 40 minutes before and after each eclipse.

 

NASA’s Juno spacecraft, currently in orbit around Jupiter, may shed some light on how the phenomenon affects the planet.

“Io spews out gases that eventually fill the Jupiter system, ultimately seeding some of the auroral features seen at Jupiter’s poles,” says Tsang in a press release. “Understanding how these emissions from Io are controlled will help paint a better picture of the Jupiter system.”

Juno Orbiter Arrives On Target


Juno Orbiter Arrives On Target

NASA’s Juno spacecraft successfully entered orbit around Jupiter on July 4, 2016, and is set to begin unlocking the mysteries of the gas giant and the origins of our solar system.

Jupiter, said Scott Bolton, Juno principal investigator from Southwest Research Institute (SwRI), “is the king of our solar system. This is it. The largest planet: more massive than all the other planets and everything else in our solar system combined, other than the sun.” He added, “What Juno’s about is looking beneath [the] surface. We’ve got to go down and look at what’s inside, see how it’s built, how deep do these features go, learn about its real secrets.”

Juno, a spin-stabilized polar-orbiting spacecraft, is only the second mission to orbit around Jupiter and the first to penetrate beneath the planet’s cloud cover to explore its interior. The spacecraft launched on an Atlas V rocket from Cape Canaveral, FL, in August 2011. It flew out past Mars, where it fired its main engine twice before looping back and getting a gravity assist from Earth that provided 70% of the velocity that the spacecraft had gotten from its launch vehicle. That extra burst of speed enabled Juno to travel all the way to Jupiter. On June 25 of this year, the spacecraft crossed the bow shock from interstellar space into the Jovian magnetic field.

A crucial moment in the mission took place days later on July 4, when the spacecraft fired up its main engine and began the process of entering orbit around Jupiter. The insertion process wasn’t simple. Due to the 48-minute lag time in communication between Juno and Earth, the entire Jupiter orbit insertion (JOI) maneuver had to be performed autonomously. In addition, the solar-powered spacecraft had to conduct the JOI while pointing away from the sun, relying on battery power. It then had to hit a target only tens of kilometers wide.

“We’re going to hit that within 1.2 seconds after a journey of 1.7 billion miles. That tells you just how good our navigation team is,” said Rick Nybakken, Juno project manager at the Jet Propulsion Laboratory (JPL), shortly before the JOI.

“To put a spacecraft in orbit around the most intense planet in the solar system, you’ve got to fire the main engine at exactly the right time, at exactly the right place. That’s not easy,” said Guy Beutelschies, director of interplanetary missions at Lockheed Martin. Despite the challenge, the maneuver was successful. “We’ve got the spacecraft pointed back at the sun and the antenna back on Earth,” he said.

Juno faced additional hazards during the insertion process, starting with exposure to the extreme radiation of Jupiter’s belts. “They’re the equivalent idea of what we have around Earth called Van Allen radiation belts, but Jupiter’s are on steroids. They’re a very serious hazard,” said Bolton.

“Juno is going to go into the scariest part of the scariest place that we know about—because we don’t know about it. It’s the part of Jupiter’s radiation environment where nobody has ever been,” said Heidi Becker, Juno’s radiation monitoring lead investigator, speaking before the JOI. “[T]hese are high-energy electrons that are so energetic they’re moving at the speed of light because Jupiter’s magnetic field has accelerated them to the point where they will go right through a spacecraft and strip the atoms apart inside your electronics.”

Knowing millions of these electrons would bombard Juno during the JOI, the team took measures to protect the spacecraft’s vital electronics and science instruments. First, the spacecraft followed a polar orbit that took it over the north pole through a less intense section of the radiation before it slid beneath the radiation belts in the equatorial region, and then exited through a section of radiation over the south pole. The spacecraft will follow a similar trajectory during its science-collection phase, which begins this fall.

“[O]ur trajectory allows Juno to fly around the really harsh parts of the radiation belts near the equator and duck underneath when we get very close to the planet. But we still have these very high-intensity regions near the planet that we can’t avoid, and later in the mission we get further and further into the equatorial region. And that’s where we’re really going to start to degrade,” said Becker.

To help shield Juno during that phase of the mission, the team built a radiation vault constructed of titanium a half-inch thick. Without that vault, said Becker, “Juno would experience something equivalent to a human being having 100 million x-rays in less than a year.” The vault reduces the radiation dose by a factor of approximately 800.

The radiation vault is one of two signature innovations for the mission. The second is the spacecraft’s massive solar arrays. Juno is the first solar-powered vehicle to operate so far from the sun. To maximize sun exposure, its solar arrays house 18,698 solar cells. Despite the fact that the spacecraft will receive only one twenty-fifth of the sunlight at Jupiter that it would on Earth, the solar arrays will provide 500 watts of power.

A second hazard during JOI was the little-known rings around Jupiter. Consisting of debris such as dust and meteorites, the horizontal rings have vertical extensions that are not well understood. The spacecraft was forced to pass through the rings during JOI with its engine door open to facilitate an uninterrupted engine burn. Had a speck of dust penetrated the forward-facing nozzle, the results could have been disastrous.

“The more you know about the mission, you know just how tricky this was. And to have it be flawless…I really can’t put it into words,” said Diane Brown, Juno program executive at NASA Headquarters.

Now in orbit around the gas giant, Juno’s first trip around Jupiter will take 53 days, as opposed to the 14-day orbit it will adopt during its science-collection phase. That phase will begin on October 19, following a final engine burn.

“And now the fun begins!” said Bolton. “The science.” The mission features nine science instruments designed to study Jupiter’s structure, atmospheric composition, gravitational and magnetic fields, polar magnetosphere, and auroras. Its findings will help answer such questions as how, when, and where Jupiter was formed, and reveal new information about the early evolution of our solar system.

Juno is managed by JPL. The spacecraft was built by Lockheed Martin Space Systems as part of NASA’s New Frontiers Program, which is managed at Marshall Space Flight Center (MSFC) for the Science Mission Directorate.

Juno’s Mission to Jupiter May Also Reveal Clues about Exoplanets


NASA’s interplanetary probe is cruising toward an encounter with our local gas giant this summer. As the data starts flowing in, we may also learn about Jupiter’s many cousins across the galaxy.

A new spacecraft is en route to the king of planets. NASA’s Juno missionwill arrive at Jupiter July 4 to study our solar system’s largest world up close and personal. Once its primary mission starts around November, Juno will spend at least a year and a half examining the planet’s interior and weather. But some scientists are interested not in what Juno can tell us about Jupiter but in what it could reveal about planets much farther away. They hope that in gathering such detailed information about our own gas-giant planet, Juno will help reveal how giant worlds beyond our own solar system were born and behave.

Scientists have already discovered hundreds of Jupiter-size planets circling other stars, and suspect those are just the tip of the iceberg. Some are known as “hot Jupiters,” because their tight orbits around their parent stars raise them to scorching temperatures. Other Jupiters circle in highly eccentric—that is, oblong—orbits, which is again unlike our own neighborhood. No one knows why some planets end up in such eccentric or close orbits whereas others—like Jupiter—revolve in relatively circular paths and from farther distances.

One theory is that planets start in different orbits and migrate over time. Juno will look for hints that Jupiter may have formed somewhere else than it is now by determining if there is less water and oxygen inside the planet than is likely if its building blocks came from its current location in the solar system. If so, the planet may have formed farther out from the sun where the environment is colder and later traveled inward. Such a finding would have implications for models predicting the formation of other gas giants in other systems. It is unlikely, however, that Jupiter has migrated very far, Juno principal investigator Scott Bolton of the Southwest Research Institute says, and he cautioned that the spacecraft will not be able to do a direct test of orbital migration, because whatever scientists learn about Jupiter’s interior, several formation scenarios may still be in play. “One theorist may update the model based on that [new] data by moving Jupiter out,” he says, “but somebody else may change the [formation] conditions and keep Jupiter where it’s at.” [See a slide show of Juno’s mission to Jupiter]

Scientists have similar questions about whether most of the gas-giant exoplanets they see formed in their current locations or moved around. Hot Jupiters, for example, do not seem likely to have formed where they are because at such proximity to stars, most of the planet-building material would have been scarce, theories suggest. Likewise, researchers have trouble understanding how gas giants can form extremely far away from their stars because of a similar lack of building blocks. Juno’s data could therefore help scientists better understand how exoplanetary systems got their layouts, says Jack Lissauer, a staff scientist at NASA Ames Research Center. Any evidence that Jupiter has migrated could support the idea that other giant planets are also likely to migrate.

Such investigations will be just part of Juno’s efforts to learn more about what Jupiter is made of. Despite 400 years of telescopic observations of the giant planet and 40 years of periodic close-up spacecraft studies, researchers still understand little about Jupiter’s formation history. Basic mysteries on whether the planet has a core—and if it does have one, the size—as well as how much water the Jovian interior holds stymie scientists.

Unlike past spacecraft sent to Jupiter, Juno is equipped with a microwave radiometer, an instrument that can measure how water vapor contributes to refracting the atmosphere at microwave frequencies, to look beneath the cloud tops to study water content and weather processes. The spacecraft will also measure Jupiter’s magnetic and gravity fields with greater precision than its predecessor, Galileo, which studied the planet and its moons between 1995 and 2003, because it will circle the planet in a polar orbit that allows it to get closer  to the planet.

Juno’s measurements of Jupiter’s magnetic field could also give insights into the planet’s internal structure. Scientists hope to learn whether deep down a core of heavy elements exists or whether the hydrogen and helium atmosphere goes “all the way down” until the elements compress at the center, Bolton says. Such a core could be helping to generate Jupiter’s magnetic field, but is not required. Scientists can also tackle the question of a core via Juno’s measurements of the planet’s gravitational field because gravitational structure can reflect the convection of heat deep inside, where the pressure is so high that compressed hydrogen acts like a molten metal.

If there is no core at all, Jupiter may have formed similarly to the sun—that is to say it may have gradually coalesced from the “protoplanetary nebula” of gas and dust that birthed our solar system. If researchers do find a core, however, that might indicate that heavy elements floating around when the solar system formed first coalesced into planet-size chunks, which then could have attracted floating gas molecules to create the giant planets Jupiter, Saturn, Uranus and Neptune.

Of course, just because scientists may get clues into how Jupiter formed does not mean they will necessarily know how other gas-giant exoplanets formed, but it is likely that our own giant planet is fairly representative, Bolton says. Jupiter, for instance, is mostly composed of hydrogen and helium, which are the elements that make up most of our solar system as well as most interstellar clouds that collapse to form other solar systems.

For the foreseeable future Juno’s observations will provide the best possible look at what a giant planet’s atmosphere is made of, said Raymond Jeanloz, an astronomy professor at the University of California, Berkeley, who studies planetary interiors. For exoplanetary researchers, however, Juno has a key limitation: It is only looking at a single world. There are thousands of known exoplanets too far away for a spacecraft to visit. Scientists are looking forward to two forthcoming space telescopes to measure the atmospheres of many giant planets: the James Webb Space Telescope and the Wide-Field Infrared Survey Telescope (WFIRST). “We are right now just barely getting our first glimpses at atmospheres” with current telescopes, says Heather Knutson, an assistant professor at the California Institute of Technology who studies exoplanetary atmospheres. “With JWST, we will see everything in beautiful detail.” WFIRST’s advantage is it will be able to view planets without the overwhelming shine of their stars drowning their own light out, due to a “coronograph” that blocks the stars’ light, she adds.

Juno will spend its first 107 days at Jupiter completing two long orbits to calibrate its instruments and then maneuver to adjust its orbital period to 14 days. The probe will then complete at least 33 of these orbits, which will allow mission scientists to eventually create a full map of Jupiter’s cloud tops and also probe beneath their surface. Funding could extend the mission slightly but the intense radiation environment of Jupiter will gradually damage Juno’s instruments and eventually force scientists to deliberately plunge the spacecraft into Jupiter before it is debilitated to the point it cannot be controlled. This measure will prevent any accidental impacts on icy and potentially life-friendly moons nearby, such as Europa, protecting them from chemical contamination by propellants as well as Earth microbes that may have hitched a ride on the spacecraft.

Five planets to align in spectacular celestial show


Mercury, Venus, Mars, Jupiter and Saturn will all appear together in the night sky for the first time since 2005

A telescope

Mercury, Venus, Mars, Jupiter and Saturn will all appear together in the night sky this month Photo: AP

Five planets will be visible in the night sky this week in a rare astronomical alignment which has not happened for more than a decade.

Mercury, Venus, Mars, Jupiter and Saturn will all appear together for the first time since 2005.

The alignment will be visible in Britain just before dawn from January 20, but astronomers say the best view is likely to be on the morning of February 5.

“There will be a dance of the planets.It will be well worth getting up for.”
Dr Robert Massey, Royal Astronomical Society

The planets will from a diagonal line from the Moon to the horizon and with clear skies and good eyesight, should be visible with the naked eye.

Dr Robert Massey of the Royal Astronomical Society said spotting Mercury would be a challenge as it will be close to the horizon, but the other planets should be easy to see in before dawn.

“There will be a dance of the planets, and now is the time to get out and have a look,” said Dr Massey. “It will be well worth getting up for.

“People will struggle to see Mercury, it will probably just look like a star but if we get good weather we should be able to see Venus, Saturn, Mars and Jupiter well. But people should have a shot at seeing them altogether.

“Venus will be very obvious in the south east and Saturn will be a little bit higher up to the right. Further over at due south, you’ll see Mars and way beyond in the south east will be Jupiter.

“They won’t be in an exact straight line, because you virtually never get that in astronomy. They will be more scattered.”

Conjunction of Mars, Jupiter and Venus seen in Newcastle upon Tyne

The five planets will be strung out in the night sky together, with Venus appearing the brightest  

Mercury will appear just three degrees above the horizon – the equivalent of three thumb widths with an outstretched arm – so will be the trickiest planet to spot.

The best time to see the alignment is around 6.45am in the morning, just before dawn. It is best to try and see Venus and then look for the rest of the planets.

Four of the five have already been visible in the early morning sky in recent weeks, but Mercury will join them for the first time on Wednesday.

Dr Massey added: “If you have binoculars you will be able to see Jupiter’s moons and the red tinge of Mars. You probably won’t be able to see Saturn’s rings but it will have a funny shape because of the rings which you should be able to pick out.

Jupiter and Venus will appear side by side over the next two nights, according to astronomers.

The planets rarely come together because of their differeing orbits

“If you are using binoculars it’s important not to look towards the sun when it rises.”

The stars Antares and Spica will also be visible in the same patch of sky. Uranus and Neptune are the only two planets that will not be on show.

And if you fail to catch the alignment this month, it will be happen again in August of this year although the late days of summer are likely to make it even more difficult to see in Britain. After that, the five planets will not be seen together again until October 2018.

People hoping to catch a glimpse of the alignment should choose an open spot, away from tall buildings and city lights to avoid light pollution.

Water geysers erupt on Europa! Could Jupiter’s icy moon host life?


Jupiter’s icy moon Europa squirts water like a squishy bath toy when it’s squeezed by the gas giant’s gravity, scientists say. Using NASA’s Hubble Space Telescope, they caught two 124-mile-tall geysers of water vapor spewing out over seven hours from near its south pole.

Water on Jupiter's moon Europa

The discovery, described in the journal Science and at the American Geophysical Union meeting in San Francisco, shows that Europa is still geophysically active – and that this world in our own solar system could hold an environment friendly to life.

“It’s exciting,” said Lorenz Roth, a planetary scientist at the Southwest Research Institute in San Antonio and one of the study’s lead authors. “The results are actually more convincing than I would have thought before.”

Europa isn’t the only squirty moon in our planetary system: Saturn’s moon Enceladus has also been caught shooting water out of its south pole in so-called tiger stripes. These pretty plumes are caused by tidal forces. Just as our moon’s gravity squeezes and stretches the Earth a bit, causing the oceans to rise and fall, Saturn’s massive gravitational pull squeezes and stretches its tiny moon, causing cracks on its icy surface to open and allowing water to shoot out.

Scientists have long wondered whether something similar was happening on Jupiter’s moon Europa. After all, its surface is about 65 million years old, which is extremely young by our solar system’s standards, little more than 1.5% of the solar system’s age. This should mean that some geophysical processes must be constantly renewing the surface.

But over several decades, researchers repeatedly failed to catch the moon in action, said Robert Pappalardo, a Jet Propulsion Laboratory planetary scientist who was not involved in the study.

When the Voyager spacecraft, launched in 1977, flew by Europa, it caught a tiny blip on the moon’s edge that people thought might be a plume, but it could not be confirmed. Then the 1989 Galileo spacecraft saw a potential plume of its own. But this turned out to be digital residue, traces of a previous image, Pappalardo said.

Even Hubble probably wasn’t able to properly see such plumes until space shuttle astronauts on the very last servicing mission for the iconic space telescope in 2009 fixed one of its cameras. Even now, looking for water vapor in the ultraviolet wavelengths of light tests the limits of Hubble’s abilities, scientists said.

To catch Europa in the act, the researchers also knew they had to time their observations right. Saturn’s icy moon, Enceladus, shoots water near the farthest point in its orbit from Saturn, when the tidal forces cause cracks at the moon’s south pole to open. Around Jupiter, Europa was probably doing the same thing.

Sure enough, when the scientists looked at Europa when it was close to Jupiter in its orbit, they saw nothing. But in December 2012, when the ice moon was at its farthest point from the gas giant, they caught a pair of plumes bearing clear signs of oxygen and hydrogen – the components of water vapor – shooting from near the southern pole.

Scientists can’t say exactly where the plumes are coming from. It could be that they’re going directly from solid ice to gas, as Europa’s ice sheets rub against each other. But it could also be that the these plumes of vapor may be coming from the ocean of liquid water thought to lie under the moon’s frozen surface.

If the moon is still geophysically active, that could make it a prime environment for life.

Another study out of this week’s American Geophysical Union meeting found signs of clays on Europa’s surface. Clays are often associated with organic matter, which is why NASA’s Mars rover Curiosity is headed to Mt. Sharp, whose clay-rich layers could hold signs of life-friendly environments.

Those clays were probably brought to Europa by comets or asteroids, and if such material was able to make it into Europa’s subsurface ocean, it could provide the nutrient-rich soup that could allow life to emerge.

“We’re trying to understand, could this be a habitable environment today? Could there be life there today?” Pappalardo said. “At Europa, it seems the processes that could permit habitability may be going on now.”

Perhaps future studies can analyze all the contents of that watery plume and see if there are any signs of organic matter, Pappalardo said. Perhaps a future mission to Europa could fly through the plume and directly sample its contents.

For now, it’s important to replicate the results, he added.

“I will sleep better knowing that there are follow-up observations that confirm it,” Pappalardo said.

Dinosaur impact ‘sent life to Mars’


Artist's impression of Chicxulub impact
The Chicxulub impact sparked a mass extinction – but did it send life hurtling into space?

The asteroid that wiped out the dinosaurs may have catapulted life to Mars and the moons of Jupiter, US researchers say.

They calculated how many Earth rocks big enough to shelter life were ejected by asteroids in the last 3.5bn years.

The Chicxulub impact was strong enough to fire chunks of debris all the way to Europa, they write in Astrobiology.

Thousands of potentially life-bearing rocks also made it to Mars, which may once have been habitable, they add.

“We find that rock capable of carrying life has likely transferred from both Earth and Mars to all of the terrestrial planets in the solar system and Jupiter,” says lead author Rachel Worth, of Penn State University.

A Hitchhikers GuideEarth rocks big enough* to support life made it to:

  • Venus 26,000,000 rocks
  • Mercury 730,000
  • Mars 360,000
  • Jupiter 83,000
  • Saturn 14,000
  • Io 10
  • Europa 6
  • Titan 4
  • Callisto 1

*3m diameter or larger.

Source: Worth et al, Astrobiology

“Any missions to search for life on Titan or the moons of Jupiter will have to consider whether biological material is of independent origin, or another branch in Earth’s family tree.”

Panspermia – the idea that organisms can “hitchhike” around the solar system on comets and debris from meteor strikes – has long fascinated astronomers.

But thanks to advances in computing, they are now able to simulate these journeys – and follow potential stowaways as they hitch around the Solar System.

In this new study, researchers first estimated the number of rocks bigger than 3m ejected from Earth by major impacts.

Europa
Could life be swimming in the oceans of Europa?

Three metres is the minimum they think necessary to shield microbes from the Sun’s radiation over a journey lasting up to 10 million years.

They then mapped the likely fate of these voyagers. Many simply hung around in Earth orbit, or were slowly drawn back down.

Others were pulled into the Sun, or sling-shotted out of the Solar System entirely.

Yet a small but significant number made it all the way to alien worlds which might welcome life. “Enough that it matters,” Ms Worth told BBC News.

About six rocks even made it as far as Europa, a satellite of Jupiter with a liquid ocean covered in an icy crust.

“Even using conservative, realistic estimates… it’s still possible that organisms could be swimming around out there in the oceans of Europa,” she said.

Travel to Mars was much more common. About 360,000 large rocks took a ride to the Red Planet, courtesy of historical asteroid impacts.

“Start Quote

I’d be surprised if life hasn’t gotten to Mars. It seems reasonable that at some point some Earth organisms made it”

Rachel Worth Penn State University

Big bang theory

Perhaps the most famous of these impacts was at Chicxulub in Mexico about 66 million years ago – when an object the size of a small city collided with Earth.

The impact has been blamed for the mass extinction of the dinosaurs, triggering volcanic eruptions and wildfires which choked the planet with smoke and dust.

It also launched about 70 billion kg of rock into space – 20,000kg of which could have reached Europa. And the chances that a rock big enough to harbour life arrived are “better than 50/50”, researchers estimate.

But could living organisms actually survive these epic trips?

“I’d be surprised if life hasn’t gotten to Mars,” Ms Worth told BBC News.

“It’s beyond the scope of our study. But it seems reasonable that at some point some Earth organisms have made it over there.”

Early Mars - artist's impression
Early Mars is thought to have been a muddy, watery world

It has been shown that tiny creatures can withstand the harsh environment of space. And bacterial spores can be revived after hundreds of millions of years in a dormant state.

Continue reading the main story

“Start Quote

I sometimes joke we might find ammonite shells on the Moon from the Chicxulub impact”

Prof Jay Melosh Purdue University

But even if a hardy microbe did stow away for all those millennia, it might simply burn up on arrival, or land in inhospitable terrain.

The most habitable places in range of Earth are Europa, Mars and Titan – but while all three have likely held water, it may not have been on offer to visitors.

Europa’s oceans are capped by a crust of ice that may be impenetrably thick.

“But it appears regions of the ice sheet sometimes break into large chunks separated by liquid water, which later refreezes,” Ms Worth said.

“Any meteorites lying on top of the ice sheet in a region when this occurs would stand a chance of falling through.

“Additionally, the moons are thought to have been significantly warmer in the not-too-distant past.”

Moon fossils

On Mars, there is little evidence of flowing water during the last 3.5bn years – the likeliest window for Earth life to arrive.

Bacillus subtilis endospores
The first space travellers? Bacterial endospores can survive for millions of years

But what if the reverse trip took place?

The early Martian atmosphere appears to have been warm and wet – prime conditions for the development of life.

And if Martian microbes ever did exist, transfer to Earth is “highly probable” due to the heavy traffic of meteorites between our planets, Ms Worth told BBC News.

“Billions have fallen on Earth from Mars since the dawn of our planetary system. It is even possible that life on Earth originated on Mars.”

While her team are not the first to calculate that panspermia is possible, their 10-million-year simulation is the most extended yet, said astrobiologist Prof Jay Melosh, of Purdue University.

“The study strongly reinforces the conclusion that, once large impacts eject material from the surface of a planet such as the Earth or Mars, the ejected debris easily finds its way from one planet to another,” he told BBC News.

“The Chicxulub impact itself might not have been a good candidate because it occurred in the ocean (50 to 500m deep water) and, while it might have ejected a few sea-surface creatures, like ammonites, into space, it would not likely have ejected solid rocks.

“I sometimes joke that we might find ammonite shells on the Moon from that event.

“But other large impacts on the Earth may indeed have ejected rocks into interplanetary space.”

Another independent expert on panspermia, Mauricio Reyes-Ruiz of the National Autonomous University of Mexico, said the new findings were “very significant”.

“The fact such different pathways exist for the interchange of material between Earth and bodies in the Solar System suggests that if life is ever found, it may very well turn out to be our very, very distant relatives,” he said.

NASA Maps Dangerous Asteroids That May Threaten Earth.


If you’ve seen films like “Armageddon,” you know the potential threat asteroids can be for Earth. To meet that threat, NASA has built a map like no other: a plot of every dangerous asteroid that could potentially endanger our planet … at least the ones we know about.

f you’ve seen films like “Armageddon,” you know the potential threat asteroids can be for Earth. To meet that threat, NASA has built a map like no other: a plot of every dangerous asteroid that could potentially endanger our planet … at least the ones we know about.

NASA released the new map of “potentially hazardous asteroids” on Aug. 2 in a post to its online Planetary Photojournal overseen by the agency’s Jet Propulsion Laboratory in Pasadena, Calif. The map shows the orbital paths of more than 1,400 asteroids known creep too close to Earth for comfort. None of the asteroids mapped pose an impact threat to Earth within the next 100 years, agency officials said.

“These are the asteroids considered hazardous because they are fairly large (at least 460 feet or 140 meters in size), and because they follow orbits that pass close to the Earth’s orbit (within 4.7 million miles or 7.5 million kilometers),” NASA officials explained in the image description. [See photos of potentially dangerous asteroids seen by NASA]

The asteroid map shows a dizzying swarm of overlapping blue ellipses (the asteroid orbits) surrounding the sun. The orbits of Earth, Venus, Mercury, Mars and Jupiter are also visible to put the asteroid orbits in perspective on a solar system-wide scale.

If you’re worried about a rogue asteroid or comet obliterating life as we know it this week, don’t panic just yet. Just because the asteroids in the new NASA map are classified as “potentially hazardous” — scientists call them PHAs in NASA-speak — that doesn’t mean they are an imminent threat to the Earth, NASA said.

According to NASA, “being classified as a PHA does not mean that an asteroid will impact the Earth: None of these PHAs is a worrisome threat over the next 100 years. By continuing to observe and track these asteroids, their orbits can be refined and more precise predictions made of their future close approaches and impact probabilities.”

NASA scientists and astronomers around the world are constantly searching for asteroids that may pose an impact threat to Earth. NASA has said that roughly 95 percent of the largest asteroids that could endanger Earth — space rocks at least 0.6 miles (1 km) wide — have been identified through these surveys.

At the Jet Propulsion Laboratory, NASA’s Asteroid Watch project scientists work to share the latest asteroid discoveries and potential threats with the public. The Asteroid Watch is part of NASA’s Near-Earth Object Program that studies asteroids and comets, as well as their potential impact threats to the Earth and other planets.

NASA released the new map of “potentially hazardous asteroids” on Aug. 2 in a post to its online Planetary Photojournal overseen by the agency’s Jet Propulsion Laboratory in Pasadena, Calif. The map shows the orbital paths of more than 1,400 asteroids known creep too close to Earth for comfort. None of the asteroids mapped pose an impact threat to Earth within the next 100 years, agency officials said.

“These are the asteroids considered hazardous because they are fairly large (at least 460 feet or 140 meters in size), and because they follow orbits that pass close to the Earth’s orbit (within 4.7 million miles or 7.5 million kilometers),” NASA officials explained in the image description. [See photos of potentially dangerous asteroids seen by NASA]

The asteroid map shows a dizzying swarm of overlapping blue ellipses (the asteroid orbits) surrounding the sun. The orbits of Earth, Venus, Mercury, Mars and Jupiter are also visible to put the asteroid orbits in perspective on a solar system-wide scale.

If you’re worried about a rogue asteroid or comet obliterating life as we know it this week, don’t panic just yet. Just because the asteroids in the new NASA map are classified as “potentially hazardous” — scientists call them PHAs in NASA-speak — that doesn’t mean they are an imminent threat to the Earth, NASA said.

Potentially Hazardous Asteroids Graphic
This graphic shows the orbits of all the known Potentially Hazardous Asteroids (PHAs), numbering over 1,400 as of early 2013.

According to NASA, “being classified as a PHA does not mean that an asteroid will impact the Earth: None of these PHAs is a worrisome threat over the next 100 years. By continuing to observe and track these asteroids, their orbits can be refined and more precise predictions made of their future close approaches and impact probabilities.”

NASA scientists and astronomers around the world are constantly searching for asteroids that may pose an impact threat to Earth. NASA has said that roughly 95 percent of the largest asteroids that could endanger Earth — space rocks at least 0.6 miles (1 km) wide — have been identified through these surveys.

At the Jet Propulsion Laboratory, NASA’s Asteroid Watch project scientists work to share the latest asteroid discoveries and potential threats with the public. The Asteroid Watch is part of NASA’s Near-Earth Object Program that studies asteroids and comets, as well as their potential impact threats to the Earth and other planets.

Space fuel crisis: NASA confronts the plutonium pinch.


The cold war plutonium reserves that fuel NASA’s deep space probes are running low. How will we power our way to the outer solar system in future?

MORE than 18 billion kilometres from home, Voyager 1 is crossing the very edge of the solar system. If its instruments are correct, the craft is finally about to enter the unknown – the freezing vastness of interstellar space. It is the culmination of a journey that has lasted 35 years.

Voyager has a nuclear tiger in its tank <i>(Image: NASA)</i>

NASA’s most distant probe owes its long life to a warm heart of plutonium-238. A by-product of nuclear weapons production, the material creates heat as it decays and this is converted into electricity to power Voyager’s instruments. Engineers expect the craft will continue to beam back measurements for another decade or so, before disappearing into the void.

Since the 1960s, this plutonium isotope has played a crucial role in long-haul space missions, mainly in craft travelling too far from the sun to make solar panels practical. The Galileo mission to Jupiter, for instance, and the Pioneer and Voyager probes all relied on it, as does the Cassini orbiter, which has revealed the ethane lakes and icy geysers on Saturn’s moons, among other wonders.

Yet despite many successes, this kind of mission may soon be a thing of the past. The production of plutonium-238 halted decades ago and the space agency’s store is running perilously low. Without fresh supplies, our exploration of the outer solar system could soon come to a grinding halt.

The problem is that plutonium-238 is neither simple nor cheap to make, and restarting production lines will take several years and cost about $100 million. Though NASA and the US Department of Energy (DoE) are keen, Congress has so far refused to hand over the necessary funds.

But there could be a better way to make it. At a NASA meeting in March, physicists from the Center for Space Nuclear Research (CSNR) in Idaho Falls proposed a radical approach that they claim should please all parties. It will be quicker, cleaner and cheaper and could offer a production line run in a commercial fashion that not only meets NASA’s needs, but also turns a tidy profit into the bargain.

So what to do? Putting the production of this material on a commercial footing, as CSNR suggests, might prove easier on the public purse, but critics are concerned this could compromise safety. Plutonium is one of the most poisonous substances known – the isotope is a powerful emitter of alpha particles and deadly if inhaled. They argue that the time and money needed to restart production would be better spent developing safer alternatives. So is this the perfect opportunity to say farewell to this cold war technology and devise new, cleaner sources of space power that could benefit us earthlings too?

Plutonium-238 has played a key role in almost all of NASA’s long-duration space missions for good reason: it produces heat through the emission of alpha particles, and with a half-life of about 87 years, the material decays slowly. Sealed into a device called a radioisotope thermoelectric generator, the decaying plutonium heats a thermocouple to create electricity. Each gram of plutonium-238 generates approximately half a watt of power. On average, NASA has used a couple of kilograms of the isotope each year to power its various craft.

It does not occur naturally. Like its weapons-grade cousin, plutonium-239, it was originally created in the reactors that made material for nuclear bombs, but US production halted when those facilities were shut down in 1988. To fill the gap, the US purchased plutonium-238 from Russia until 2009, when a contract dispute ended the supply. With Russia now also running short, it is doubtful that any new deal will be struck.

So the US government must decide whether or not to resume production. According to a 2009 report by the US National Research Council, NASA has access to about 5 kilograms of the stuff, which could last it until the end of the decade (see diagram). Officials at the DoE say that if they get the go-ahead now, 2 kilograms could be made annually by 2018 – just in time to restock NASA’s cupboards. But funding is proving hard to come by. NASA has agreed to share the burden and released about $14 million for studies to work out the costs of restarting the production line – which would most likely be at Oak Ridge National Laboratory in Tennessee. However, costs could eventually spiral to $150 million, suggest some at the research council, and Congress seems loath to provide any funding directly to the DoE.

Clearly, making plutonium-238 is an expensive business. The conventional way to produce it involves placing a batch of neptunium-237 inside a powerful nuclear reactor and irradiating it with neutrons for up to a year (see diagram). The sample must then be put through a series of purification steps to separate plutonium-238 from the other fission products that also form.

At the NASA Innovative Advanced Concepts (NIAC) symposium in March, however, Steven Howe of CSNR proposed what could be a simpler and cheaper way to make it. The trick is to use a mechanical feed line, a coiled pipe surrounding the reactor core. Small capsules containing just a few grams of neptunium-237 are pushed continuously along this pipe, each one spending just days in the reactor. As they pop out the other end, the plutonium-238 is extracted and the remaining neptunium-237 is sent through the line again. About 0.01 per cent of the neptunium is converted on each pass, so this cycle would need to be repeated thousands of times to create the kilos of material required by NASA.

This technique brings some significant advantages, including shorter irradiation times causing far fewer fission products to be generated. This simplifies the subsequent chemical separation steps and reduces the amount of radioactive waste. In addition, it can work in small reactors that are far cheaper to run than the powerful national lab facilities that are required for the batch processing of old. Howe even envisions operating along commercial lines, so NASA and the DoE would just purchase the final product, rather than footing the bill for the entire production process.

The CSNR team working on this concept is already funded by a $100,000 NIAC grant and has submitted a proposal to build a prototype feed line and to demonstrate that they can mechanically push the capsules through it, as well as perform the subsequent separation steps. Howe believes they can have their process up and running in just three years, at a cost of about $50 million – half the proposed cost of restarting conventional production – and could create about 1.5 kilograms of plutonium-238 each year.

Though the team still has to determine the optimum irradiation time, operating the process continuously instead of converting several kilograms in batches twice a year should help keep costs and the facility size down. And if they charge $6 million per kilogram – less than the latest Russian asking price – this process would be cost-effective for private industry, Howe says. “Like commercial space travel, we’re doing commercialised plutonium production,” he says.

Whether or not Howe’s technique saves money, or even makes it, breathing fresh life into plutonium production is not popular with everyone. Plutonium-238 is highly toxic, and an accident during or after launch could release it into the atmosphere. In 1964, for example, a US navy navigation satellite re-entered the atmosphere and broke up, dispersing 1 kilogram of plutonium-238 around the planet, roughly double the amount released into the atmosphere by weapons testing. Though the plutonium’s containers have been redesigned to survive re-entry intact, the Cassini probe’s near-Earth fly-by in 2006 triggered widespread public protests. Restarting plutonium production is “a very frightening possibility”, says Bruce Gagnon of the Global Network Against Weapons and Nuclear Power in Space based in Brunswick, Maine. “It obviously indicates that the nuclear industry views space as a new market,” he says. “It’s like playing Russian roulette.” Gagnon is also worried by the prospects of a commercialised production line. “When you introduce the profit incentive, you start cutting corners,” he says.

Then there are concerns over proliferation and political capital. While plutonium-238 cannot be used to make a nuclear weapon, it is a different story with neptunium-237. This is weapons-grade material: bombarded by fast neutrons, it is capable of sustaining a chain reaction without unstable heat decay. Edwin Lyman at the Union of Concerned Scientists based in Cambridge, Massachusetts, believes that given these safety and security issues, non-nuclear power generation systems should be a priority for space applications. “Alternatives need to be explored fully,” he says. “If the US proceeds with the restart, it will be more difficult for us to dissuade other countries from doing the same, should they decide they need to produce their own plutonium-238 supply.”

Can sunlight help fill the gap? The intensity of light drops with distance from the sun, following an inverse square law, so sending solar-powered spacecraft to the outer planets looks like a non-starter. In Pluto’s orbit, for example, it would take a solar array of 2000 square metres to generate the same amount of power as a 1-square-metre array in Earth’s orbit. Nevertheless, in August 2011, NASA launched Juno, the first mission to Jupiter using solar energy instead of plutonium. Juno relies on three 10-metre-long solar panels to gather the power it needs to operate. And according to a 2007 NASA report, solar-powered missions beyond Jupiter are not out of the question.

What’s needed, says James Fincannon of NASA’s Glenn Research Center, are new solar cells that can cope with the extreme conditions in the outer solar system. Great strides are being made in developing lightweight, high-efficiency solar cells, he says. If the cost and mass of these arrays can be reduced further, and if a spacecraft’s power needs can be reduced to less than 300 watts – about half that of the Galileo probe – Fincannon suggests that a craft powered by a 250-square-metre solar array could operate as far away as Uranus. Gagnon agrees. “For years we’ve said that solar would work even in deep space,” he says.

There are even plutonium-free ways to power craft exploring the darker reaches of the solar system where Fincannon’s arrays would not work. At the NIAC symposium where Howe discussed his plutonium production process, Michael Paul of Pennsylvania State University’s Applied Research Laboratory described a novel engine that could power craft on the surface of cloud-wrapped worlds where little sunlight penetrates.

Take Venus. Paul proposes combining lithium fuel with carbon dioxide from the greenhouse-planet’s atmosphere, and burning it to provide heat for a Stirling engine – a heat pump that uses a temperature difference to drive a piston linked to a generator (see “Cloud power”). The system would not need nuclear launch approval, could operate at very high power levels and could be modified to work on Titan, Mars or even in the permanent dark of the moon’s south pole, he says. With further development Paul believes the technology could be ready to launch by 2020. “I see this power system as a way to enable a whole new set of opportunities that are closed off because we just don’t have enough plutonium,” he says.

Paul admits that his lithium-powered landers would last just a fraction of the decades-long lifetime achievable using plutonium. “Fifty years of work has shown that there are applications where there are no alternatives – period,” says Ralph McNutt of the Johns Hopkins University Applied Physics Laboratory. But, he adds, “to the extent that there are alternatives to radioactive power sources, we should take them”. Fincannon agrees: “It is always a good time to come up with alternative power sources,” he says.

Besides, spending money developing lightweight solar cells or more efficient Stirling engines could offer benefits on, as well as off, Earth. Engineers are already exploring ways to turn metal powder into fuel for vehicle engines, and Paul suggests his technology could help expand underwater exploration missions, too. The same can no longer be said for plutonium-238. Once used to power cardiac pacemakers, security and health concerns mean that the material is no longer welcome.

So which way will NASA jump? Howe remains determined to fight in plutonium’s corner and recently presented his case to the agency. As far as space is concerned, this power struggle isn’t over yet.

When this article was first posted, it contained an incorrect reference to Isaac Newton

Cloud power

Solar power is not an option for landers heading through thick clouds like those surrounding Venus. That’s where the generator conceived by Michael Paul and his team at Pennsylvania State University comes in. Paul’s team suggest powering a Venus lander by burning lithium with carbon dioxide sucked in from the planet’s atmosphere – eliminating the need to carry along an oxidiser with the fuel.

The heat from combustion would drive a small turbine or Stirling engine, which would power the lander’s electronics. But on boiling-hot Venus, the biggest challenge is keeping the lander’s electronics cool. Paul predicts that four-fifths of the engine’s power output will go towards pumping heat away from the craft’s electronics. Previous missions to Venus have lasted no more than 2 hours beyond touchdown before their batteries petered out. Paul calculates that 200 kilograms of lithium will be enough to keep sensors running for a week.

He believes that adding the planet’s carbon dioxide to lithium is the only way to pack enough punch to power a Venus lander. To provide electrical power and cooling for a week-long mission would otherwise require 850 kilograms of batteries, for instance, or 50 plutonium-powered generators. Even NASA’s colossal Cassini probe – “the flagship of all flagship missions” – doesn’t have that many, says Paul.