On Sept. 29, NASA’s Juno probe will perform its closest flyby to Jupiter’s icy moon Europa in more than 20 years, as the spacecraft begins its mission to probe the depths of Europa’s ice to find pockets of liquid water.
Europa Contains a global ocean under a solid crust of ice, which makes this satellite one of the most interesting places on Earth solar system to search for alien life and one of Top priorities for astrobiologists. While Juno can’t tell us whether Europa hosts alien life, it will tell us more about the moon’s ice crust, such as how thick it is and whether there are any pockets of liquid water that can reach the surface.
Juneau arrive Jupiter In July 2016, its mission focused on Study Jupiter’s Atmospherefrom the heights of the reddish-brown cloud tops to the depths of lower clouds hundreds of miles below, and understanding the gas giant’s powerful magnetic field and its internal structure, all the way to its core.
In 2021, NASA granted Juno an extension and gave it a new goal: to study some Jupiter’s moons. In June 2021, the spacecraft flew within 645 miles (1,038 kilometers) of Earth Ganymede, with a diameter of 3,273 miles (5,268 kilometers), is the largest moon in the solar system. Next, it will be Europa’s turn, and Juno will fly past the moon just 220 miles (355 kilometers) above Europa’s surface. Juno won’t see the entire moon, but only a small portion of the surface. However, Juno’s cameras have a wide field of view — a bit like that of a smartphone camera — allowing the spacecraft to capture more landscapes than normal cameras.
related: Jupiter’s Ganymede, largest moon in the solar system, looks stunning in first photo of NASA’s epic Juno flyby
staring under the ice
Juno’s work on Europa is thought to be NASA’s upcoming ‘reconnaissance mission’ Europa Clippers Scott Bolton, vice president of Space Science and Engineering at Southwest Research Institute and principal investigator of the Juno mission, told Space.com. “But we’ll still be doing a lot of scientific work in Europa.”
The key to that science will be Juno’s Microwave Radiometer (MWR). “This is a new type of instrument we’ve invented to look under Jupiter’s clouds,” Bolton said. “‘But we can apply the same instruments to icy moons and look at the ice a little bit.”
Operating at six wavelengths, the MWR can detect thermal radiation below the ice surface. The depth to which it can detect this emission depends on the level of impurities in the ice. The purer the ice, the deeper the MWR can “see”.
Although the findings from Juno’s Ganymede flyby Still writing, Bolton revealed that when Juno pointed the MWR at Ganymede, the instruments confirmed that the giant moon had a very thick icy crust.
Europa may be a different story, at least in some parts of the moon. Scientists hope to one day drill through the ice and into the moon’s dark subsurface ocean. The ice crust is expected to be 19 miles (30 kilometers) deep, at least in most areas, but may be thinner in some areas.
related: Chaos emerges in detailed new view of Jupiter’s icy moon Europa
Previous missions to image Europa— Voyager One and Voyager 2 spaceship and Galileo orbiter – Parts of the lunar surface were found to be stained with material that appeared to gush from below. Juno’s infrared cameras and spectrometers will analyze the material’s composition to determine whether it’s made of salts or organic molecules.
One theory is Water pockets can form underground, either liquid rises through convection through the ice shell, or the ice in the shell melts, possibly as a result of the pressure exerted on the ice by Jupiter’s gravitational tides. The MWR should be able to tell if there are pockets of water near the surface.
“When we developed Juno, we didn’t really think about getting close to the icy moon; we were totally focused on Jupiter,” Bolton said. “Now that we’re looking for satellites for our extended mission, it’s clear that microwave radiometers are working on icy objects as well as gas giant, so I believe it will become the mainstream workhorse of planetary exploration in the future. “
Related to the possibility of liquid water close to the surface is controversial Evidence of geyser eruptions Water that rises above the surface and into space. year 2013, Hubble Space Telescope Plumes of hydrogen and oxygen clouds (which produce water when they combine) were detected, and possible outlines of these plumes were seen in 2016. Scientists studying archived data from the Galileo spacecraft have found that it measured subtle disturbances in Jupiter’s magnetosphere close to Europa, likely the result of charged particles in the plume deflecting the giant planet’s magnetic field.
In 2021, scientists Sufficient water vapor detected Released over Europa, it only takes a few minutes to fill an Olympic-sized swimming pool. How this water vapor got there, however, remains uncertain, as scientists have so far failed to confirm the existence of the geyser.
Could Juno have first confirmed detection of geysers during the flyby? “It was a long shot,” Bolton said. “If plumes do exist, then we must be lucky enough to have them extinguished as we fly by, and they must be where we happen to see.”
Still, even if Juno doesn’t spot a moving plume, the spacecraft may see a geological feature on the surface that is releasing water vapor, similar to “tiger stripes” superior Saturnice moon Enceladus Unleash your own geyser. Alternatively, Juno’s navigation cameras will look for ice particles drifting back to Europa’s surface, reflecting and scattering light.
Juno’s polar orbit around Jupiter, flyby Arctic Then there’s the south pole, meaning it will approach Europa from a high inclination, giving the spacecraft its first view of the moon’s polar regions. In contrast, previous missions embraced the satellite plane and focused on their equatorial regions. Juno’s orbit also means it’s the spacecraft’s only chance to see Europa up close.
“What’s happening is that Juno’s orbit is now being distorted by Jupiter’s gravitational field,” Bolton said. “We always cross the equator, but as we get closer to Jupiter, the point where we cross the equator is moving inward.”
Juno will cross Jupiter’s equator in the summer of 2021 at a distance of Ganymede (665,000 miles, 1.07 million kilometers). Now, the spacecraft is crossing Jupiter’s equator at the distance of Europa – 383,000 miles (617,000 kilometers).And in December 2023 and February 2024, Juno will cross Jupiter’s equator at the distance of its volcanic moons Aio — 262,000 miles (422,000 km) — and two close flybys within 932 miles (1,500 km).
Juno’s extended mission will run until 2025, at which point mission scientists will have to assess whether the spacecraft has enough propellant to keep pointing its antennae Earth And the state is good enough to continue, or if the task must end.
“I think NASA will accept another extension if the spacecraft is healthy,” Bolton said.
The main problem is radiation. Juno’s orbit around the giant planet is elliptical, and each time it reaches the perijove (meaning its closest point to Jupiter), it receives a massive dose of radiation from the charged particles trapped in it. Jupiter’s powerful magnetosphere And often pound the surface of the planet’s moons.To protect against this radiation, the Juno was built “like an armored tank with a shield,” Bolton said, “but in the end, our shields won’t work anymore. Star Trek Language, radiation will begin to damage Juno’s electronics. “
Juno’s encounter with Europa may be its only shot, but it won’t be the last spacecraft to visit Jupiter’s icy moon.NASA’s long-awaited Europa Clipper mission is Scheduled to launch in October 2024 and arrives in orbit around Jupiter in April 2030. The Europa Clipper will perform nearly 50 close flybys of Europa to fully characterize the moon, and follow up with Juno in the subterranean search for pockets of liquid water that may support life. Meanwhile, the European Space Agency’s probe to Jupiter’s icy moons (juice) will launch in April 2023 and arrive at Jupiter in July 2031 to perform studies on Europa, Ganymede and Callisto.
Follow Keith Cooper on Twitter @21stCenturySETI.follow us on twitter @Spacedotcom and on Facebook.