Jupiter's moon Europa might be able to support life even if there's little or no volcanic activity under the satellite's icy shell, a new study suggests.

A salty ocean of liquid water is believed to lie beneath Europa's icy exterior. Scientists think this ocean could be habitable, if it harbors the required chemical building blocks and the right proportion of elements to provide energy for biological systems — the right ratio of oxygen to hydrogen, for example.

The new study suggests that there is, indeed, enough of that energy. A research team led by Steve Vance, of NASA's Jet Propulsion Laboratory in Pasadena, California, found that, even without taking possible volcanic processes into account, Europa likely produces 10 times more oxygen than hydrogen, just as Earth does.

According to the team's calculations, Europa's hydrogen is generated as seawater reacts with rock in the moon's crust. Europa has cooled slowly over the eons, forming new cracks in the crust that expose more rock to seawater, thus generating more hydrogen, the researchers said.

Until now, many planetary scientists thought that Europa, kneaded by Jupiter's gravity, would be volcanically active. After all, the neighboring moon Io is the most volcanically active body in the solar system; Jupiter's gravity and tidal forces deform Io's crust and mantle, generating huge amounts of heat.

Something similar could be happening at Europa, but nobody knows for sure if it is. Much speculation about possible Europan life envisions a biosphere that resembles the clusters of life found near hydrothermal vents on Earth's ocean floor. But the new research suggests that volcanism isn't necessary to cycle chemicals through the ocean, and thus is probably not necessary for living things to survive, study team members said.

The study was published online last week in the journal Geophysical Research Letters.

You can Follow Jesse Empsak @Mad_Science_Guy. Follow us @Spacedotcom, Facebook or Google+. Originally published on Space.com.

Just one month before the Juno spacecraft arrives at the gas giant Jupiter, the most detailed radio-wave maps ever of the planet's atmosphere dig beneath surface-level clouds to reveal the whirling ammonia flows that help form its distinctive features.

Researchers used the upgraded Very Large Array (VLA) radio telescope in New Mexico to probe 60 miles (100 kilometers) below the top of the gas giant's pervasive clouds — revealing a correlation between the colorful whirls and spots on the visible surface and the movement of gas below, which is driven by Jupiter's internal heat source.

"We in essence created a three-dimensional picture of ammonia gas in Jupiter's atmosphere, which reveals upward and downward motions within the turbulent atmosphere," Imke de Pater, an astronomer at the University of California, Berkeley, and lead author on the new work, said in a statement. [Amazing Photos of Jupiter and Its Many Moons]

Transition from optical image of Jupiter to new radio map; many of the same features are visible. In the radio view, rising ammonia-rich gases are dark and sinking, ammonia-poor gases are bright. Clouds of condensed ammonia are not visible by radio.

Those maps reveal more detail than any previous radio map, spotting features just 800 miles (1,300 km) across, UC Berkeley officials said in the statement.

The researchers saw that ammonium-rich gases rose to form the upper cloud layers — ammonium hydrosulfide at about 200 Kelvin (minus 100 degrees Fahrenheit) and a cloud of ammonia-ice at 160 K (minus 170 degrees F), both of which can be seen with optical telescopes, officials said in the statement. The map also revealed gases with less ammonia sinking back down into the planet.

The areas with less ammonia, spread in a broad band around the planet, seem to correlate with "hot spots" on the planet's surface — areas that researchers have pinpointed as particularly bright in radio and infrared images. Those "hot spots" appear as holes in the planet's cloud cover, and look hazy in optical light.

"With radio, we can peer through the clouds and see that those hotspots are interleaved with plumes of ammonia rising from deep in the planet, tracing the vertical undulations of an equatorial wave system," Michael Wong, an astronomer who is also at UC Berkeley, said in the statement.

To build the new map, the researchers observed the many different wavelengths of radio waves emitted by the planet's atmosphere over time. While visible-light telescopes can get back images from the surface quickly, the VLA radio telescope has to observe for multiple hours. The telescope's upgraded sensitivity, combined with new data-processing algorithms, let the researchers unblur the smeared images that are made by the fast-moving planetary atmosphere. Those images can be combined with the Hubble Space Telescope's visible views of the planet and others to get a fuller view of the environment.

"We now see fine structure in the 12- to 18-gigahertz band, much like we see in the visible, especially near the Great Red Spot, where we see a lot of little, curly features," Wong said, referring to the massive storm on Jupiter's surface that's two times Earth's diameter. "Those trace really complex upwelling and downwelling images there."

On July 4, NASA's Juno spacecraft will reach Jupiter and begin studying its weather, composition and magnetic environment before diving down through the planet's deep atmosphere. These new Jupiter maps will help researchers fit those findings into the bigger picture of the planet.

The new work was detailed June 2 in the journal Science.

Email Sarah Lewin at slewin@space.com or follow her @SarahExplains. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.

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A spectacular new image of Pluto shows rugged mountains, nitrogen-ice plains and, perhaps, a big cloud scudding through the dwarf planet's exotic skies. NASA even described the view as the "twilight zone" of Pluto.

NASA's New Horizons spacecraft captured the photo shortly after its closest approach to Pluto on July 14, 2015, when the sun was on the other side of the dwarf planet from the probe's perspective.

In the backlit twilight view, sunlight filters through Pluto's many-layered atmosphere and lights up certain features, including the towering Norgay Montes mountain range and the vast plain known as Sputnik Planum, whose surface is likely renewed every 500,000 years or so by churning convective processes.

Also illuminated is a bright wisp tens of miles across "that may be a discrete, low-lying cloud in Pluto's atmosphere; if so, it would be the only one yet identified in New Horizons imagery," NASA officials wrote in a photo description Thursday (June 2) that dubbed the image Pluto's "twilight zone." "Atmospheric models suggest that methane clouds can occasionally form in Pluto's atmosphere."

These features — mountains, plains and possible cloud — all lie in a sliver of sunlight, at the top limb of Pluto. But intriguing landscape details are also visible near the bottom of the photo, which depicts Pluto's night side.

"The topography here appears quite rugged, and broad valleys and sharp peaks with relief totaling 3 miles (5 kilometers) are apparent," NASA officials wrote.

New Horizons took the newly released photo with its Ralph/Multispectral Visual Imaging Camera about 19 minutes after closest Pluto approach, from a distance of about 13,400 miles (21,550 km). (Closest approach brought the probe within 7,800 miles, or 12,550 km, of the dwarf planet's surface.)

Extreme Close-Up View of Pluto's Surface | View

https://youtu.be/LwIgHyHoXxA

New Horizons' Extreme Close-Up of Pluto’s Surface (no audio)

https://youtu.be/pK9nbK1Jc4s

NASA releases spellbinding details of Pluto’s surface

https://youtu.be/PIscO1djgIA

The photo features a resolution of about 1,400 feet (430 meters) per pixel, NASA officials said.

New Horizons is still beaming flyby data home, and will continue to do so through this coming fall. (The probe is currently about 3.2 billion miles, or 5.15 billion km, from Earth; such a vast distance makes transmission rates slow, due to the significant weakening of New Horizons' radio signal.)

The spacecraft is currently zooming toward a small object called 2014 MU69, which lies about 1 billion miles (1.6 billion km) beyond Pluto. If NASA approves and funds a proposed extended mission, New Horizons will study 2014 MU69 up close on Jan. 1, 2019.

Follow Mike Wall on Twitter @michaeldwall and Google+. Follow us @Spacedotcom, Facebook or Google+. Originally published on Space.com.

EDITOR'S RECOMMENDATIONS

• New Horizons Probe's July 14 Pluto Flyby: Complete Coverage
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What was thought to be an underwater, lost city is actually a naturally occurring geological phenomenon.

Pipe-like, disc and doughnut-shaped structures discovered by underwater divers near the island of Zakynthos, Greece, were originally believed to be ruins of an ancient city, such as remnants of paved floors, courtyards and columns.

Now researchers have found that the "ruins" are in fact geological formations, the results of a natural phenomenon that took place in the Pliocene epoch, up to 5 million years ago. [See Photos of the 'Lost City' Geological Formations]

Scientists now know the universe is expanding, at an ever-increasing rate. So if it's ballooning, what is it growing into? In other words, what is beyond the known universe?

Defining this "beyond the universe" would imply that the universe has an edge. And that's where things get tricky, because scientists aren't certain if such a drop-off exists.

The answer depends on how one views the question.

Cliff-hanger

One form of the question asks, "Could you go somewhere that you could look 'beyond' the universe," the way one might peer beyond a cliff edge or look out a window to see the outside of a building? The answer to that query is "probably not."

One reason involves the "cosmological principle," said Robert McNees, an associate professor of physics at Loyola University Chicago. The cosmological principle states that the distribution of matter in any part of the universe looks roughly the same as in any other part, regardless what direction you look in; in scientists' terms, the universe is isotropic.

The cosmological principle is, in part, a consequence of the idea that the laws of physics are the same everywhere. "There's lots of local variation — stars, galaxies, clusters, etc. — but averaged over big chunks of space, no place is really that different than anywhere else," McNees told Live Science in an email

The implication though, is that there is no "edge"; there is no place to go where the universe just ends and one could look in some direction and see what's beyond it.

One analogy often used to describe this edgeless universe is the surface of a balloon. An ant on such a surface can walk in any direction and it would look like the surface was "unbounded" — that is, the ant might come back to where it started but there would be no end to the journey. So even though the surface of a balloon is a finite number of square units, there's no edge to it, no boundary (since you can go forever in any one direction). In addition, there's no "center," so there's no preferred point on the balloon's spherical surface.

The universe is a three-dimensional version of the balloon's skin.

Ballooning universe

But how can the universe be expanding if there is no end or edge to it?

Using the balloon analogy again, if one were to add more air to the balloon, the ant would observe other things on the balloon's surface getting farther away. And the greater the distance between the ant and some object, the faster that object would be receding. But no matter where the ant skittered, the speed at which those objects were receding would follow the same relations — if the ant came up with an equation describing how fast the farthest objects were receding, it would work the same way anywhere on the balloon's surface.

However, balloons, when blown up, are expanding into a three-dimensional space. The problem is that this doesn't apply to the universe. By definition, the universe contains everything, so there is no "outside." Physicist Stephen Hawking has often said that the whole question makes no sense, because if the universe came from nothing and brought everything into existence, then asking what lies beyond the universe is like asking what is north of the North Pole. [The Big Bang to Civilization: 10 Amazing Origin Events]

Dr. Katie Mack, a theoretical astrophysicist at the University of Melbourne in Australia, told Live Science that it might be more useful to think of the universe as getting less dense, rather than expanding. That is, the concentration of matter in the universe is decreasing as the universe expands, she said.

That's because galaxies aren't moving away from each other through space — it's space itself that is getting bigger. So any aliens in the galaxies that humans see would all come to the same conclusion that Earthlings do: Everything else is moving away in all directions, and the local galaxy is at rest.

Because space is expanding, it's possible for the galaxies to appear as if they are moving faster than light, without violating relativity — which says that nothing can go faster than light in a vacuum. The actual size of the observable universe is 46 billion light-years in any direction, even though the universe began only 13.8 billion years ago, Mack said. But that still sets a limit on the size of the universe humans can see, called the observable universe. Anything outside of that radius of 46 billion light-years is not visible to Earthlings, and it never will be. That's because the distances between objects in the universe keep getting bigger at a rate that's faster than the light beams can get to Earth.

And on top of that, the rate of expansion has not been uniform. For a brief fraction of a second after the Big Bang, there was a period of accelerated expansion called inflation, during which the universe grew at a much faster pace than it is growing now. Whole regions of space will never be observable from Earth for that reason. Mack noted that assuming inflation happened, the universe is actually 10²³ times bigger than the 46 billion light-years humans can see. So if there is an edge to the universe, it's so far away Earthlings can't see it, and never will. [Big Bang, Deflated? Universe May Have Had No Beginning]

An infinite space?

Meanwhile, there's the issue of whether the universe is infinite in space to begin with, which Mack said is still an open question. Or, the universe might wrap around itself in a higher dimension in the same way that the 2D surface of a sphere wraps around itself in three dimensions, she said.

An additional factor is whether the universe popped into existence out of nothing at all, via small fluctuations in a vacuum, or, as Hawking and James Hartle proposed, time and space become interchangeable close to the beginning. If either one is the case, then asking what came before the universe and what is outside of it makes no sense.

Mack said there are ongoing attempts to resolve the question of whether the universe is like a sphere, curving back on itself so that if you travel in one direction you eventually return to your starting point.

"We look for repeated spots in the sky," she said. "That's what people look for when seeking evidence for the universe being finite. … Our space could be a 3D space embedded in a four-dimensional space." (The universe has four dimensions that humans interact with, three of space and one of time, but this would imply there is an additional, fourth spatial dimension.)

If astronomers found two places on opposite sides of the sky that were exactly the same, that would be a strong indication that the universe is curved in that way. There are no guarantees, though. While some cosmological theories such as string theory posit higher dimensions, most of those would be "rolled up" and small, whereas a curved universe's "extra" space dimension would have to be large.  

All of this means that if there's an end to the universe, humans might well never be able to see it, and there is the real possibility that the universe is shaped so that it can't have a boundary to begin with. 

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