Jupiter, the largest and most massive planet in our solar system, may be its own worst enemy. It turns out that its central core may in fact be self-destructing, gradually liquifying and dissolving over time. This implies it was previously larger than it is now, and may dissolve altogether at some point in the future. Will Jupiter eventually destroy itself completely? No, probably not, but it may lose its heart…
The core is composed of iron, rock and ice and weighs about ten times as much as Earth. That’s still small though, compared to the overall mass of Jupiter itself, which weighs as much as 318 Earths! The core is buried deep within the thick atmosphere of hydrogen and helium. Conditions there are brutal, with a temperature of about 16,000 kelvin – hotter than the surface of the Sun – and a pressure about 40 million times greater than the atmospheric pressure on Earth. The core is surrounded by a fluid of metallic hydrogen which results from the intense pressure deep down in the atmosphere. The bulk of Jupiter though is the atmosphere itself, hence why Jupiter (and Saturn, Uranus and Neptune) are called gas giants.
One of the primary ingredients in the rock of the core is magnesium oxide (MgO). Planetary scientists wanted to see what would happen when it is subjected to the conditions found at the core; they found that it had a high solubility and started to dissolve. So if it is in a state of dissolution, then it was probably larger in the past than it is now and scientists would like to understand the process. According to David Stevenson of the California Institute of Technology, “If we can do that, then we can make a very useful statement about what Jupiter was like at genesis. Did it have a substantial core at that time? If so, was it 10 Earth masses, 15, 5?”
The findings also mean that some exoplanets which are even larger and more massive than Jupiter, and thus likely even hotter at their cores, may no longer have any cores left at all. They would be indeed be gas giants in the most literal sense.
The conditions inside Jupiter’s core can’t be duplicated in labs yet, but the spacecraft Juno should provide much more data when it arrives at and starts orbiting Jupiter in 2016.
All these worlds are yours except Europa Attempt no landing there Use them together use them in peace
Despite that famous cryptic warning in the film 2010: The Year We Make Contact, NASA is planning for a possible attempted landing on Jupiter’s moon Europa. This is a mission that many people have been hoping for, since Europa is believed to have a liquid water ocean beneath the icy surface (as well as lakes within the surface crust itself), making it a prime location in the search for life elsewhere in the solar system. Two landers are being proposed which would launch in 2020 and land about six years later.
As stated by Kevin Hand of JPL, “Europa, I think, is the premier place to go for extant life. Europa really does give us this opportunity to look for living life in the ocean that is there today, and has been there for much of the history of the solar system.”
While the landers wouldn’t be able to access the ocean water which is well below the surface, they could analyze the surface composition with a mass spectrometer, seismometers and cameras. The mass spectrometer could detect organics on the surface if there are any. The landers probably wouldn’t last too long though, because of the intense radiation from Jupiter on the unprotected surface (as Europa has only a very slight, tenuous atmosphere). Accessing any of the water from its ocean or lakes would require drilling deep down, something for a more advanced future mission.
Another mission being considered is a Europa orbiter, which could also launch in 2020. In some ways that might be even better, as it could provide a broader detailed study of the moon over a longer time period. Of course if both missions could be done, that would be fantastic, but budgets will probably only allow for one of them. The lander mission is estimated to probably cost about $800 million to $2 billion, while an orbiter would cost about $4.7 billion.
It might be noted that a return mission to Saturn’s moon Enceladus would also be possible, especially since the water from its subsurface ocean or sea (depending on the various working models of its interior and geology) can be sampled directly from its water vapour geysers, no need to drill down. The Cassini spacecraft has already done that more than once, and has found organics of various complexities, but Cassini’s instruments can’t detect life itself.
Either destination would be exciting, as both are thought to be two of the most likely places in the solar system, besides Earth of course, to be inhabitable or even possibly inhabited. Everywhere on Earth where there is water, there is life. That may or may not be true for Europa or Enceladus, but we’ll never know unless we look.
Artist's impression of New Horizons' encounter with Pluto and Charon. Credit: NASA/Thierry Lombry
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It may not have noticed anything different as it continued its high-speed trek through interplanetary space, but today New Horizons passed a new milestone: it is now (and will be for quite some time) the closest spacecraft ever to Pluto!
This breaks the previous record held by Voyager 1, which came within 983 million miles (1.58 billion km) of the dwarf planet on January 29, 1986.
New Horizons has been traveling through the solar system since its launch on January 19, 2006 and is now speeding toward Pluto at around 34,500 mph (55,500 km/hr). It has thus far traveled for 2,143 days and is just over halfway to the distant icy world.
“Although we’re still a long way — 1.5 billion kilometers from Pluto — we’re now in new territory as the closest any spacecraft has ever gotten to Pluto, and getting closer every day by over a million kilometers.”
– Alan Stern, New Horizons Principal Investigator
A gravity boost obtained by a close pass of Jupiter in 2007 gave the spacecraft the extra speed needed to make it to Pluto by 2015. (Without that, it wouldn’t have been reaching Pluto until 2036!)
Achievements like this are wonderful indicators that New Horizons is alive and well and that its historic goal is getting increasingly closer every day.
Diagram of the Pluto-Charon encounter in July 2015 (NASA/APL)
“We’ve come a long way across the solar system,” said Glen Fountain, New Horizons project manager at the Johns Hopkins University Applied Physics Laboratory (APL). “When we launched it seemed like our 10-year journey would take forever, but those years have been passing us quickly. We’re almost six years in flight, and it’s just about three years until our encounter begins.”
See answers to some FAQs about Pluto
New Horizons will pass by Pluto and its moons on July 14, 2015, becoming the first spacecraft ever to visit the distant system. It will image Pluto’s surface in unprecedented detail, resolving features as small as 200 feet (60 meters) across.
New Horizons will not land or enter orbit around Pluto but instead quickly pass by and continue on into the Kuiper Belt, where even more distant frozen worlds await. The New Horizons team is currently investigating further exploration targets should its mission be extended.
Credit: Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute (JHUAPL/SwRI)
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In recent years, it has become surprisingly apparent that, contrary to previous belief, Earth is not the only place in the solar system with liquid water. Jupiter’s moon Europa, and possibly others, are now thought to have a deep ocean below the icy crust and even subsurface lakes within the crust itself, between the ocean below and the surface. Saturn’s moon Titan may also have a subsurface ocean of ammonia-enriched water in addition to its surface lakes and seas of liquid methane. Then of course there is another Saturnian moon, Enceladus, which seems to not only have liquid water below its surface, but huge geysers of water vapour and ice particles erupting from long fissures at its south pole, which have been sampled directly by the Cassini spacecraft. Even some asteroids may have liquid water layers beneath their surfaces. There is also still a chance that Mars might have subsurface aquifers.
But now there is another contender which at first thought might seem to be the most unlikely place to find water – Pluto.
Inhabiting the bitterly cold, lonely outer reaches of the solar system, this dwarf planet would hardly seem to be a good place to look for liquid water, but new research is indicating that, like the other moons already mentioned, it may yet surprise us. It is now being suggested that a subsurface ocean is not only possible, but likely.
The New Horizons spacecraft is scheduled to fly by Pluto in 2015, and it may be able to confirm the existence of the ocean if it is actually there. As it is understood right now, Pluto has a thin shell of nitrogen ice covering a thicker shell of water ice. But is there a layer of liquid water below that? The way for New Horizons to help to determine that is to study the surface features and shape of Pluto as it passes. If there is a noticeable bulge toward the equator, then that means that any primordial ocean or liquid layer probably froze a long time ago, since a liquid layer would tend to cause the surface ice to flow, reducing any bulge. This is based on the fact that a spherical body, as it rotates, will push material toward the equator by angular momentum. If there is no bulge, then any liquid layer is probably still liquid today.
The surface itself can also provide clues about what lies beneath. If there are large fractures, as there are on Europa and Enceladus, their characteristics can be an indication of whether there is an ocean down below. The fractures are caused by surface stresses; tensional stresses would result from icy water beneath the outer ice shell while compressional stresses would indicate a solid layer instead. The long fractures on Europa are particularly reminiscent of the cracked ice floes in Antarctica on Earth where an ice layer covers the sea water beneath it. If geysers similar to those on Enceladus were to be seen on Pluto, that would also of course be good evidence for an ocean.
There is also, inevitably, the question of life. If Pluto’s rocky interior contains radioactive isotopes such as potassium, as seems likely, they could provide enough heat to maintain an ocean. “I think there is a good chance that Pluto has enough potassium to maintain an ocean,” said planetary scientist Francis Nimmo from the University of California at Santa Cruz, who is involved with the new studies. And if you have liquid water and heat… Pluto, however, is thought to lack organics, which would be necessary as a starting point for life.
A Plutonian ocean? Who would have ever thought? When New Horizons finally reaches Pluto in 2015, we should hopefully have a better idea one way or the other regarding this intriguing possibility.
In 1989, meteorologists discovered sprites. Not the spirits, elves, or pixies that pepper Shakespearean comedies but their equally elusive electrical namesakes. Lightning sprites are large scale electrical discharges inside the clouds above storms that make the upper atmosphere glow, sort of like a fluorescent lightbulb.
Meteorologists have already determined that sprites likely aren’t unique to Earth. In fact, this elusive form of lightning might be common throughout the solar system. Now, researchers at Tel Aviv University are asking whether the presence of sprites on other planets could indicate the presence of organic material in their atmospheres.
The layers of our atmosphere. Image credit: National Weather Service, JetStream Online School for Weather.
Though not an uncommon phenomena, sprites are incredibly hard to find and observe. They can only be captured with highly sensitive high speed cameras. Sprites occur in the Earth’s Mesosphere, layer between the stratosphere and the thermosphere – about 50 km (31 miles) to 90 km (56 miles) high. At this altitude, the gases that make up our atmosphere are much thinner and unable to hold heat from the Sun making the average temperature a chilly 5°F (-15°C) to as low as -184°F (-120°C).
But gases at this altitude are still thick enough to slow meteors – this is where they burn up and create what we see as meteor showers. Gases in the mesosphere are also thick enough to light up with sprites, providing a window into the composition of our atmosphere. Sprites, which glow reddish-orange, indicate the kinds of molecules present in this layer of the atmosphere.
Lightning isn’t a rare occurrence in our solar system, which leads researchers to suspect sprites might be found on Jupiter, Saturn, and Venus – all planets with the right environment for strong electrical storms. Just like on Earth, sprites found on these planets could open a window in their atmospheric composition, conductivity, and possibly point to the presence of exotic compounds.
Jupiter and Saturn present the most exciting environments. Both gas giants experience lightening storms with flashes more than 1,000 as powerful as those found on Earth. It’s on these planets that Ph.D. student Daria Dubrovin, with her supervisors Prof. Colin Price of Tel Aviv University’s Department of Geophysics and Planetary Sciences and Prof. Yoav Yair at the Open University of Israel, is focussing on.
Dubrovin has re-created these planetary atmospheres in a lab to study the presence of sprites in space. Or, as she describes her work, “We make sprites in a bottle.” She hopes this will provide a new understanding of electrical and chemical processes on other planets.
A sprite as it might appear in Saturn's atmosphere, created in a TAU lab. Image credit: American Friends, Tel Aviv University
What’s more, understanding lightning on other worlds could help researchers understand the possibility of life on other worlds. As Dubrovin points out, lightning is commonly accepted as the generator of organic molecules that turned early Earth’s ocean into the life-filled primordial soup. Increased study of lightning on other planets could give another clue into the presence of extraterrestrial life. Their research could easily be applied to exoplanets, not just bodies in our solar system.
A lightning storm on Saturn has Dubrovin pretty excited. It’s currently producing over 100 electrical flashes per second, a rare occurrence even within the planet’s volatile cloud layers. If researchers could successfully gather images of higher altitude sprites from the Cassini spacecraft (currently in orbit around Saturn), it would not only yield information on the storm below but also add to the general knowledge base of sprites and lightning on other planets.
A new video created by NASA’s Solar System Exploration Division answers one of the most frequently asked questions about our planetary neighbor, in just 60 seconds.
Passage of of 2005 YU55 near Altair from 6:03 p.m. – 6:12 p.m. EST (11:03 – 11:12 UTC)
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It’s already been stated several times here on Universe Today that 2005 YU55, a 400-meter-wide roughly spherical asteroid, will not pose any threat to Earth as it passes by on Tuesday, November 8… even though it will come within 80% of the distance to the Moon. Many experts have come forward to state this fact, including Don Yeomans of JPL’s Near-Earth Object Observation Program and Lance Benner, a radio astronomer with the Deep Space Network in Goldstone, CA. But it will still be a notable event, being the first time since 1976 such a large object will pass so closely by our planet. So, with the eve of YU55’s approach upon us, let’s turn our curiosity toward another aspect of this cosmic visitation: how can we see it?
Unfortunately there are a couple of factors working against the casual observer being able to witness YU55’s pass. One: it’s a dark object. A very dark object. 2005 YU55 is a C-type asteroid, which means it is composed of carbonaceous material and is thus effectively darker than coal, reflecting less than 1% of the sunlight that it receives. It probably won’t be brighter than magnitude 10. (On the backwards-ranked scale of apparent magnitude, 6 is the limit of best visibility to the average human eye, while -1 or 0 would be a very bright star. Jupiter is about -3 right now, while the full moon would be -12.7. In a typical suburban neighborhood 3 or 4 is the limit of naked-eye visibility.)
And two: the Moon will be close to full on the night of the 8th, and YU55 will be headed in its direction. That sure won’t help visibility.
But, should you be located in a dark area, and should you have a 6″ or larger telescope at your disposal, you may want to give a go at spotting the asteroid that’s caused quite a fuss over the past few months for yourself. It won’t be a simple task, but it’s not impossible – and to help you out teacher, writer and astronomy enthusiast David Dickinson has posted an article about it on his blog, Astro Guyz.
Here’s an exerpt:
Closest approach to Earth occurs at 11:29 UTC/06:29 EST at about 202,000 miles distant, placing it high to the southwest for observers on the US Eastern Seaboard. At its closest approach, 2005 YU55 will glide along at one degree every 7 minutes, easily noticeable after a few minutes of observation at low power. I plan to target selected areas with my GOTO mount, sketch the field, then watch for changes. I may also take some wide-field piggyback stills with the DSLR, but mostly, this one will just be fun to watch.
Visually tracking a Near-Earth asteroid can be thrilling to watch; for example, I’ve actually seen 4179 Toutatis years ago show discernable movement after tracking it for a few moments in the eyepiece!
– David Dickinson
Wide field finder of 2005 YU55 from sunset until 8:30PM EST.
The asteroid will pass through the constellations Aquila, Delphinus, and Pegasus as it heads westward. Interestingly, 2005 YU55 passes within a degree of Altair centered on 6:07:30PM EST only 27 minutes after local sunset, and also makes a very close pass of the star Epsilon Delphini during closest approach. These both make good visual “anchors” to aim your scope at during the appointed time and watch. Keep in mind, the charts provided are rough and “Tampa Bay-centric…”
On an approach as close as this one, two factors muddle the precise prediction coordinates of the asteroid; one is the fact the gravitational field of the Earth will change the orbit of 2005 YU55 slightly, and two is that the position will change due to the position of the observer on the Earth and the effect of parallactic shift. Many prediction programs assume the Earthly vantage as a mere point in space, fine for positioning deep sky objects but not so hot for ones passing near the planet. A good place to get updated coordinates is JPL Horizons website which lets you generate an accurate ephemeris for your exact longitude latitude and elevation.
David goes on to add:
2005 YU55 will pass our Moon at 8 AM Universal Time on November 9th at a distance only marginally closer than it did the Earth, at 140,000 miles. Interestingly, it also transited Sun on November 3rd as seen from the Moon, but would have appeared <1” in size, a tough target for any would-be lunar-based observer. Its next close predicted passage of the Earth won’t be until 2056 at nearly 3 times the distance.
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Excellent information… many thanks to David for sharing with us! (You can read the full article on his website here.) And if you do witness the pass of this asteroid and somehow manage to get some photos of it, you can share them on the Universe Today Flickr group… they may be featured in an upcoming article!
The cracked ice surface of Europa. Credit: NASA/JPL
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Until fairly recently, the search for life elsewhere in the solar system has focused primarily on Mars, as it is the most Earth-like of all the other planets in the solar system. The possibility of finding any kind of life farther out in the outer solar system was considered very unlikely at best; too cold, too little sunlight, no solid surfaces on the gas giants and no atmospheres to speak of on any of the moons apart from Titan.
But now, some of the places that were previously considered the least likely to hold life have turned out to be perhaps some of the most likely to provide habitable environments. Moons that were thought be cold and frozen for eons are now known to be geologically active, in surprising ways. One of them is the most volcanically active place known in the solar system. At least two others appear to have oceans of liquid water beneath their surfaces. That’s right, oceans. And geysers. On the surface, they are ice worlds, but below, they are water worlds. Then there’s the one with rain, rivers, lakes and seas, but made of liquid methane instead of water. Billions of kilometres farther out from the Sun than the Earth. Who would have thought? Let’s look at those last three in a bit more detail…
Ever since the film 2001: A Space Odyssey first came out, Europa has been the subject of fascination. A small, icy moon orbiting Jupiter, its depiction in that movie, as an inhabited world beneath its ice crust was like a sort of foreshadowing, before the Voyager and Galileo spacecraft gave us our first real close-up looks of this intriguing place. Its surface shell of ice is covered with long cracks and fissures, giving it an appearance much like ice floes at the poles on Earth. More surprising though, was the discovery that, also like on Earth, this ice cover most likely is floating on top of a deep layer of liquid water below. In Europa’s case though, the water layer appears to cover the entire moon, a global subsurface ocean. How is this possible? If there is liquid water, there must be heat (or high concentrations of salts or ammonia), and if you have water and heat, could there be something living in those waters? Gravitational tugging from Jupiter indeed appears to provide enough heat to keep the water liquid instead of frozen. The environment is now thought to be similar to ocean bottoms on Earth. No sunlight, but if there are volcanic vents generating heat and minerals, as on Earth, such a spot could be ideal for at least simple forms of life. On Earth, places like these deep in the oceans are brimming with organisms which don’t require sunlight to survive.
Water vapour geysers on Enceladus. Credit: NASA/JPL
Then there’s Enceladus. Another very small icy moon, orbiting Saturn. Geological activity was considered very unlikely on such a tiny world, only a few hundred kilometres in diameter. But then Cassini saw the geysers, plumes of material erupting from the south polar region through large, warmer cracks nicknamed “tiger stripes.” Cassini has now flown directly through the geysers, analyzing their composition, which is mostly water vapour, ice particles, salts and organics. The latest analysis based on the Cassini data indicates that they almost certainly originate from a sea or ocean of liquid water below the surface. Warm, salty water loaded with organics; could Enceladus be another possible niche for extraterrestrial life? As with Europa, only further missions will be able to answer these questions, but the possibilities are exciting.
Radar image of one of many methane lakes on Titan. Credit: NASA/JPL
Titan is even more fascinating in some ways, the largest moon of Saturn. It is perpetually shrouded in a thick smoggy atmosphere of nitrogen and methane, so the surface has never been visible until now, when Cassini, and its small lander probe Huygens, first looked below the smog and clouds. Titan is like an eerily alien version of Earth, with rain, rivers, lakes and seas, but being far too cold for liquid water (not much heat here), its “water cycle” is composed of liquid methane/ethane. Appearance-wise, the surface and geology look amazingly Earth-like, but the conditions are uniquely Titan. For that reason, it has long been considered that the chances of any kind of life existing here are remote at best. In the last few years however, some scientists are starting to consider the possibility of life forming in just such environments, using liquids other than water, even in such cold conditions. Could life occur in a liquid methane lake or sea? How would it differ from water-based life? Last year, a discovery was made which might be interpreted as evidence of methane-based life on Titan – a seeming disappearance of hydrogen from the atmosphere near the surface and a lack of acetylene on the surface. Previous theoretical studies had suggested that those two things, if ever found, could be evidence for methane-based lifeforms consuming the hydrogen and acetylene. All of this is still highly speculative, and while a chemical explanation is probably more likely according to the scientists involved, a biological one cannot be ruled out yet. Future proposed missions for Titan include a floating probe to land in one of the lakes and a balloon to soar over the landscape, pursuing such mysteries as never before. How cool is that?
Oh, and the moon that is the most volcanically active place in the solar system? Io, although with the only known forms of liquid there being extremely hot lavas on that sulfuric hothouse, the chances of life are still thought to be unbelievably slim. But that’s ok when you start to find out that worlds with oceans and lakes, etc. may be much more common than previously imagined…
When the first spacecraft flew by Mars in the 1960’s, the images returned revealed a relatively uninteresting-looking place, featureless in some areas and pockmarked with craters in most others. It looked a lot like the Moon. Later flybys and orbiting probes, however, gave us a closer look at other regions on the planet, providing a glimpse of what Mars is really like: a world of mountains, volcanoes, canyons, craters, old riverbeds and polar ice caps. It is little surprise then, that these striking geologic features captured scientists’ attention the most, and so areas like Hesperia Planum, a flat, relatively dull-looking plain, have received less attention over the years.
But there is a mystery in this region in the form of geologic features called rilles. No one has been able to figure out where they came from or how they formed.
The rilles in Herperia Planum are a series of about a dozen narrow, sinuous channels. They are up to a few hundred meters wide, and hundreds of kilometers long, but don’t appear to have any sources or destinations. The assumption has been that they were most likely created by lava flows, like their counterparts on the Moon. But apart from one very small volcano, there is little evidence of any volcanism in Hesperia Planum, which makes the appearance these rilles difficult to explain.
Another explanation could be water, but again, there are no obvious sources or other indications of past water in this region.
These enigmatic features have been the subject of study by scientists from the University at Buffalo, State University of New York. Geologist Tracy Gregg and her student Carolyn Roberts have been comparing them to rilles on the Moon, and their preliminary findings were presented today at the Annual Meeting of The Geological Society of America, in Minneapolis, and they hope to find some answers in further study and collaboration with other scientists.
“On the Moon we see these same kinds of features and we know that water couldn’t have formed them there,” Gregg said. “Everybody assumed these were huge lava flows, But if it turns out to be a lake deposit, it’s a very different picture of what Mars was doing at that time.”
So, were they formed by water, lava or something else? If it turned out to be water, that would of course be more interesting in terms of the search for possible habitable areas in Mars’ past.
Whichever explanation turns out to be correct, or even a different one, it will be one more piece of evidence which helps to further our understanding of this fascinating world, so much like our own in some ways, yet utterly alien in others
The paper is available here and additional photos are here.
This 88-gram (3.5 oz.) meteorite broke through the roof of the Comette family
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When your last name is Comette, I’m sure the occasional astronomy-themed joke is never far away. But it’s no joke that the Comette family living in Draveil, a suburb south of Paris, was paid a visit by a real extraterrestrial a couple of weeks ago – in the form of an 88-gram (3.5 oz.) meteorite that broke through their roof!
The Comettes were on vacation at the time, so didn’t realize their house had been struck by a space rock until they noticed a leak in the roof. When they called in a roofer it was discovered that a thick tile had been completely broken through.
The meteorite was found wedged in insulation.
Mineral scientist Alain Carion investigated the meteorite and determined that it’s an iron-rich chondrite, a 4.57-billion-year-old remnant of the early Solar System that most likely came from the main asteroid belt between the orbits of Mars and Jupiter. About 3/4 of all meteorites that have been observed landing on Earth are chondrites.
While obviously not impossible, the odds of your home being hit my a meteorite are incredibly slim. Only 145 meteorites have been documented landing in the US in the past 200 years. On March 26, 2003, just before midnight, hundreds of fragments of a large meteorite fell in the Park Forest area of Chicago. Several fell through roofs of houses and one punched a hole in the roof of the fire station. One large piece weighing about 2.5 kg (5.5 lb) crashed into a bedroom, narrowly missing a boy who was asleep in his bed! On September 23, 2003, a 20 kg (44 lb) stone meteorite tore straight through a two-storey house in New Orleans and came to rest in the basement. (Source: University of New Mexico Institute of Meteoritics.)
Only about 50 meteorites have been found in France over the past four centuries, and none has ever before been discovered less than 80 km (50 miles) from Paris.
While they could attempt to sell the meteorite that struck their home, possibly fetching several hundred euros for it, the Comettes have decided to keep their otherworldly visitor.
“A piece of the history of space of which we know nothing, but which is fascinating, has fallen on us,” Mrs. Comette told the Le Parisien newspaper. “It’s like a fairytale, and less likely than winning the lottery, we’re told.”
