Jupiter’s icy moon, Europa, is a prime candidate in the search for life elsewhere in our Solar System — but landing a spacecraft on the moon may be even more difficult than we thought.
Certain patches of ice on Europa could be rough and jagged, resembling sharp blades, according to a new modeling. And that may make it hard for future probes to touch down gently on the surface.
It’s possible that conditions in areas around Europa’s equator may be just right to form what are known as “penitentes.” These are unique ice formations found here on Earth in places like the Andes Mountains.
Penitentes form on Earth when super-cold ice sits in direct sunlight for long periods of time, causing patches in the ice to turn directly from a solid to a gas.
In a new study, published today in Nature Geoscience, researchers found that the exact conditions needed to create this phenomena are present on parts of Europa too.
Scientists still hope to confirm the finding with visual evidence of penitentes on Europa. But the new model is a key piece of information that could help inform NASA’s future missions.
Right now, the space agency is working on two different missions to the moon.
The first, Europa Clipper, is slated to launch sometime around 2022 and will send a spacecraft to fly by Europa and possibly zoom through the world’s plumes — suspected geysers that spew water from a vast ocean below the moon’s icy crust.
In the meantime, NASA is in the very early stages of designing a lander that could also travel to Europa someday, touch down on the surface, and then drill into the ice. That way, it could potentially sample the unseen water below.
But if parts of the surface are truly shaped like blades, it would be extremely hazardous for a conventional lander. This new research could help NASA decide which areas to avoid when considering landing spots on Europa.
And it’s possible that the upcoming Europa Clipper mission will get even more detailed images of the moon’s surface, to confirm if these formations are actually there.
“We’re really hoping that the Clipper mission will tell us one way or the other,” Daniel Hobley, a geologist and planetary scientist at Cardiff University in the UK, as well as lead author on the study SAID.
“We should be able to take pictures of good enough quality to prove it.”
However, answers will come soon with Europa Clipper, which will fly within 16 miles of Europa’s surface. The spacecraft also has a camera and instruments with higher resolution than Galileo had.
“It will be flying over the equatorial region, which is where these features are predicted to exist,” Phillips says. “I think Europa Clipper is well-suited to see any actual evidence for these formations.”
Even if ice blades are found, it’s not a showstopper for a future lander. The new study only found these high sublimation rates occurring in a narrow band around the equator, but areas closer to the poles don’t seem to have the same conditions.
“There are still lots of places on the surface of Europa that would be really interesting potential landing sites that are well outside of this band,” says Phillips. “There’s no reason to shoot for the equator over anywhere else.”
Jupiter has the strongest magnetic field of any of the planets in the solar system. Like the field that shelters Earth, it’s essentially dipolar, which means it has a north pole and a south pole, like the field created by a bar magnetic.
A really, really big bar magnetic.
Earth’s magnetic field is produced by churning liquid iron in the planet’s outer core. Iron conducts electricity, and a changing electrical current creates a magnetic field.
So as the liquid iron cycles up and down, carrying heat from the planet’s center up to the mantle and then sinking again, it creates powerful electrical currents that in turn produce the planet’s global field.
But Jupiter doesn’t have an iron core. In fact, it’s unclear if it has a core at all — Juno’s observations suggest the core might be “fuzzy,” a concentration of rock and ice that has dissolved (or is still dissolving) into the surrounding hydrogen.
Instead, the source of the global field is the overlying mantle of metallic hydrogen, where hydrogen molecules trade electrons, creating currents. The planet’s rotation organizes the resulting magnetic field into a dipole.
Or, at least it kind of does. Reporting in the September 6th Nature, Kimberly Moore (Harvard) and colleagues have discovered a strange plume of magnetic field shooting up from a region in Jupiter’s northern hemisphere and reentering the planet at its equator.
And it’s three times stronger than the main dipole field.
Detecting the Invisible
As it flies around Jupiter, the Juno spacecraft measures the planet’s magnetic field using two instruments called fluxgate magnetometers.
At each magnetometer’s core lie two rings, made of a material that soaks up magnetic field. Think of it like a magnetic sponge. Like a sponge, the material can only hold so much before it saturates.
The scientists can magnetically “fill up” the rings by running current through wires coiled around them, first one direction, then the other, explains John Connerney (NASA Goddard Space Flight Center), who heads up Juno’s magnetometer investigations and is a coauthor on the new study.
But if there’s another magnetic field in the environment, the rings will soak it up, too.
That will reduce how much of the applied field the rings can absorb from the wires in one direction, but increase the amount absorbed from current flowing the other direction.
When the magnetometer cancels out this imbalance using another wire-wound structure around each of the rings, the instrument measures how strong the environmental field is based on how much current it takes to push the field in the rings back to zero.
The coils’ orientations give the external field’s direction. But the magnetometer only detects the magnetic field the spacecraft is flying through.
The researchers have to extrapolate from those measurements, using detailed calculations to map the field at the planet’s cloudtops and below.
Combining data from eight of Juno’s flybys, the scientists confirmed the existence of the bizarre magnetic feature, hints of which had shown up in an analysis last year from Juno’s first orbit.
The structure looks like a ponytail shooting out from the planet’s forehead and reentering through the nose, at a location the team is calling the Great Blue Spot (for its color in a map of the planet’s field).
There’s nothing like this ponytail in the southern hemisphere. Why does this magnetic ponytail exist? Scientists don’t know.
The team considers several ideas in their paper, the most likely being that there’s some sort of layering in the metallic hydrogen mantle that’s messing with the convection pattern.
Layering could naturally arise with a dissolving core: Rock and ice mixed in with hydrogen would raise the density, and if that mixing isn’t uniform, it could create layers of different density that could destabilize the cyclic convection patterns or spur different convection patterns in distinct layers.
Nearly 41 years after lifting off, NASA’s historic Voyager mission is still exploring the cosmos.
The twin spacecraft launched several weeks apart in 1977 — Voyager 2 last Aug. 20 and Voyager 1 last Sept. 5 — with an initial goal to explore the outer solar system.
Voyager 1 flew by Jupiter and Saturn, while its twin took advantage of an unusual planetary alignment to visit Jupiter, Saturn, Uranus and Neptune.
And then the spacecraft kept on flying, for billions and billions of miles. Both remain active today, beaming data home from previously unexplored realms.
Indeed, in August 2012, Voyager 1 became the first human-made object ever to reach interstellar space.
The mission’s legacy reached into film, art and music with the inclusion of a “Golden Record” of Earth messages, sounds and pictures designed to give any prospective alien who encountered it an idea of what humanity and our home planet are like.
This time capsule is expected to last billions of years.
The spacecraft are now flying through space far away from any planet or star; their next close encounter with a cosmic object isn’t expected to occur for 40,000 years.
Their observations, however, are giving scientists more insight into where the sun’s influence diminishes in our solar system, and where interstellar space begins.
Voyager 1 is nearly 13 billion miles (21 billion kilometers) from Earth and has spent five years in interstellar space.
This zone is not completely empty; it contains material left over from stars that exploded as supernovas millions of years ago.
The “interstellar medium” (as the space in this region is called) is not a threat to Voyager 1. Rather, it’s an interesting environment that the spacecraft is studying.
Voyager 2 is nearly 11 billion miles (18 billion km) from Earth and will likely enter interstellar space in a few years, NASA officials have said.
Its observations from the edge of the solar system help scientists make comparisons between interstellar space and the heliosphere.
When Voyager 2 crosses the boundary, the two spacecraft can sample the interstellar medium from two different locations at the same time.
Mission designers made the spacecraft robust to make sure they could survive the harsh radiation environment at Jupiter.
This included so-called redundant systems — meaning the spacecraft can switch to backup systems if needed — and power supplies that have lasted well beyond the spacecraft’s primary mission.
Each of the spacecraft is powered by three radioisotope thermoelectric generators, which convert the heat produced by the radioactive decay of plutonium-238 into electricity.
The power available to each Voyager, however, decreases by about 4 watts per year.
This requires engineers to dig into 1970s documentation (or to speak with former Voyager personnel) to operate the spacecraft as its power diminishes.
Even with an eye to efficiency, the last science instrument will have to be shut off around 2030, mission team members have said.
But even after that, the Voyagers will continue their journey (albeit without gathering data), flying at more than 30,000 mph (48,280 km/h) and orbiting the Milky Way every 225 million years.
If signs of life exist on Jupiter’s icy moon Europa, they might not be as hard to find as scientists had thought, a new study reports.
The 1,900-mile-wide (3,100 kilometers) Europa harbors a huge ocean beneath its icy shell.
What’s more, astronomers think this water is in contact with the moon’s rocky core, making a variety of complex and intriguing chemical reactions possible.
Researchers therefore regard Europa as one of the solar system’s best bets to harbor alien life.
Europa is also a geologically active world, so samples of the buried ocean may routinely make it to the surface—via localized upwelling of the ocean itself, for example, and/or through geyser-like outgassing, evidence of which has been spotted multiple times by NASA’s Hubble Space Telescope.
NASA aims to hunt for such samples in the not-too-distant future. The agency is developing a flyby mission called Europa Clipper, which is scheduled to launch in the early 2020s.
Clipper will study Europa up close during dozens of flybys, some of which might be able to zoom through the moon’s suspected water-vapor plumes.
And NASA is also working on a possible post-Clipper lander mission that would search for evidence of life at or near the Europan surface.
It’s unclear, however, just how deep a Europa lander would need to dig to have a chance of finding anything.
That’s because Europa orbits within Jupiter’s radiation belts and is bombarded by fast-moving charged particles, which can turn amino acids and other possible biosignatures into mush.
That’s where the new study comes in.
NASA scientist Tom Nordheim and his colleagues modeled Europa’s radiation environment in detail, laying out just how bad things get from place to place.
They then combined these results with data from laboratory experiments documenting how quickly various radiation doses carve up amino acids (a stand-in here for complex biomolecules in general).
The researchers found significant variation, with some Europan locales (equatorial regions) getting about 10 times the radiation pounding of others (middle and high latitudes).
At the most benign spots, the team determined, a lander would likely have to dig just 0.4 inches (1 centimeter) or so into the ice to find recognizable amino acids.
In the high-blast zones, the target depth would be on the order of 4 to 8 inches (10 to 20 cm).
That latter range is still quite manageable, said Nordheim, who’s based at the California Institute of Technology and NASA’s Jet Propulsion Laboratory, both of which are in Pasadena.
That’s good news for the potential lander mission, Nordheim added: With radiation exposure seemingly not a limiting factor, planners can feel free to target the areas of Europa most likely to harbor fresh ocean deposits—the fallout zone beneath a plume, for example—wherever they may lie.
Scientists still haven’t identified any such promising touchdown areas; the Europa imagery captured to date just hasn’t been sharp enough. But Europa Clipper’s work should change things, Nordheim said.
“When we get the Clipper reconnaissance, the high-resolution images—it’s just going to be a completely different picture,” he said. “That Clipper reconnaissance is really key.”
Ten more moons have been confirmed to orbit around Jupiter, bringing the planet’s total known satellite count to 79.
That’s the highest number of moons of any planet in the Solar System. And these newly discovered space rocks are giving astronomers insight as to why the Jupiter system looks like it does today.
Astronomers at Carnegie Institution for Science first found these moons in March 2017, along with two others that were already confirmed in June of last year.
The team initially found all 12 moons using the Blanco 4-meter telescope in Chile, though finding these objects wasn’t their main goal.
Instead, they were searching for incredibly distant small objects — or even planets — that might be lurking in our Solar System beyond Pluto.
But as they searched for these fringe space rocks, they decided to take a peek at what might be lurking around Jupiter at the same time.
Now, the moons they found have been observed multiple times, and their exact orbits have been submitted for approval from the International Astronomical Union, which officially recognizes celestial bodies.
These moons are all pretty tiny, ranging between less than a mile and nearly two miles wide. And they break down into three different types. Two orbit closer to Jupiter, moving in the same direction that the planet spins.
Farther out from those, about 15.5 million miles from the planet, there are nine that revolve in the opposite direction, moving against Jupiter’s rotation.
But in this same distant region, one strange moon that astronomers are calling Valetudo is moving with Jupiter’s spin, like the two inner moons.
That means it’s going in the opposite direction of all the other moons in the same area. “It’s basically driving down the highway in the wrong direction,” Scott Sheppard, an astronomer at Carnegie who led the discovery team said.
“That’s a very unstable situation. Head-on collisions are likely to happen in that situation.”
Valetudo isn’t the only moon of Jupiter that acts this way. Another moon called Carpo also orbits far out from Jupiter, moving in the opposite direction of many other moons in the area.
However, Valetudo orbits much farther away than Carpo, and it may actually be the smallest moon Jupiter has.
Now with this discovery, astronomers think it’s good evidence that moon-on-moon collisions have happened in Jupiter’s past, and these are responsible for the lunar landscape around the planet today.
“Valetudo, at just 1 kilometer across, is probably the last remnant of a much larger moon that’s been ground down into dust over time,” says Sheppard.
Finding moons around Jupiter can be tough. As the biggest planet in our Solar System, it has a very large area of influence, so there’s a lot of space where moons could potentially be.
It’s difficult to search that area in a timely manner with a telescope. “It’s like looking through a straw, and you’re just covering as many points around Jupiter as you can looking for these things,” says Sheppard.
And since Jupiter is so large, it reflects a whole lot of light. That means there can be a lot of glare when searching for super faint moons around the planet.
Europa is an ice-encrusted moon of Jupiter with a global ocean flowing underneath its surface. NASA is planning a mission soon that will look for signs of possible life there.
Now, a new finding from old data makes that mission even more tantalizing.
In recent years, the Hubble Space Telescope has spotted what looks like plumes, likely of water vapor, reaching more than 100 miles above the surface.
The plumes, if they exist, could contain molecules that hint at whether Europa possesses the building blocks of life.
In a study published Monday in the journal Nature Astronomy, scientists are reporting a belated discovery that Galileo, an earlier NASA spacecraft that studied Jupiter, appears to have flown through one of the Europa plumes more than 20 years ago.
And that occurred close to one of four regions where Hubble has observed plumes.
“That’s too many coincidences just to dismiss as ‘There’s nothing there’ or ‘We don’t understand the data,’” said Robert T. Pappalardo, the project scientist for NASA’s upcoming Europa Clipper mission, which may launch as soon as 2022.
“It sure seems like there’s some phenomenon, and plumes seem consistent.”
Galileo, which launched in 1989, arrived at Jupiter in 1995 and spent almost eight years examining the planet and its moons until its mission ended with a swan dive into Jupiter in 2003.
During a flyby of Europa on Dec. 16, 1997, instruments on Galileo measured a swing in the magnetic field and a jump in the density of electrons. At the time, scientists noted the unusual readings, but they did not have an explanation.
Then, in 2005, another spacecraft passing by another moon around another planet made a startling observation.
NASA’s Cassini spacecraft — which completed its mission last September — found geysers of ice crystals erupting out of Enceladus, a small moon of Saturn. Enceladus, it turns out, also has an ocean of liquid water under its ice.
That spurred renewed curiosity about Europa and whether it too might burp bits of its ocean into space. The Hubble first recorded signs of possible plumes in 2012, then again in 2014 and 2016.
But at other times, Hubble has looked and seen nothing. That suggests the plumes are sporadic.
Last year, Melissa A. McGrath, a senior scientist at the SETI Institute in Mountain View, Calif. who was not involved in the new study, took a look at some radio experiments conducted by Galileo which examined how signals bent as Europa passed between Earth and the spacecraft.
The experiments showed Europa possesses an atmosphere.
Astronomers will certainly be taking more looks at Europa with the Hubble, trying to better understand how often the plumes erupt.