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.