Closing in on Jupiter: 7 Fun Facts About Juno's Mission — **Artist's illustration of NASA's Juno spacecraft arriving at Jupiter on July 4, 2016.**
**Credit: NASA**

NASA's Juno spacecraft will reach Jupiter Monday (July 4) after a five-year journey through deep space. The probe will study the structure and evolution of the solar system's largest planet from orbit, taking measurements for more than a year despite Jupiter's intense radiation environment.

"Jupiter is the planet on steroids in our solar system; everything about it is extreme," Juno principal investigator Scott Bolton, of the Southwest Research Institute in San Antonio, told Space.com.

The mission has several major science goals. One is to learn how much water is inside Jupiter, which should yield insights about the amounts of water that were present in the solar system's early days. [Juno's Jupiter Arrival: Complete Coverage]

Juno scientists also hope to map out Jupiter's interior, determining (among other things) whether or not the planet has a rocky core. Such information should help researchers learn more about the planet-formation process in general, shedding light on the nature of worlds throughout the Milky Way galaxy, mission team members have said.

"It's a big challenge," Bolton said, "but we have to take those challenges if we're going to explore and learn about ourselves, and how we fit into nature."

Here are seven things to know about Juno's mission:

1. Jupiter's radiation will take a toll on Juno

Juno is scheduled to orbit Jupiter for about 20 months. The spacecraft likely can't keep going much longer than that, because of the intense radiation environment at Jupiter.

For example, the planet's magnetic field is about 20,000 times as intense as Earth's, so Juno will have to withstand impacts by many charged particles moving at superfast speeds. [Juno's Jupiter Mission Fraught with Danger (Video)]

That's not to say that NASA isn't doing its best to keep the probe safe. Juno harbors a radiation-shielded electronics vault, the first of its kind. The vault is a cube about the size of an SUV's trunk, made of titanium about 0.3 inches (0.8 centimeters) thick. Inside are some of the most precious parts of Juno — its brain (command and data-handling box), its power and distribution unit, and 20 other key electronics components, according to a NASA press kit. With instruments inside, the vault has a mass of about 500 lbs. (200 kilograms).

2. Juno only has about as much hard-drive space as your laptop

The spacecraft's main computer has about as much memory as a laptop with a solid-state drive. The computer features 256 megabytes of flash memory — to preserve data even in the event of a power interruption — and 128 megabytes of dynamic random-access memory (DRAM). DRAM is useful in situations where low cost and high capacity are required at the same time, NASA officials have said.

Why not give Juno more memory? The spacecraft uses the BAE Systems RAD750 single-board computer, which is designed for high-radiation environments. This computer has been used many times in space, including for NASA missions such as the Van Allen probes (which fly through Earth's radiation belts), the Mars Reconnaissance Orbiter and the Mars rover Curiosity.

Juno: Inside NASA's mission to Jupiter

https://youtu.be/Z1jkNC8IR1Y

3. Juno is the most distant solar-powered spacecraft ever

Juno has gone farther into deep space than any other solar-powered probe. The spacecraft set the record in January, when it was about 493 million miles (793 million kilometers) from the sun, surpassing the distance of the European Space Agency's Rosetta spacecraft during the latter's journey to Comet 67P/Churyumov-Gerasimenko.

Most spacecraft that venture so far from the sun need to use nuclear power to keep going. But Juno is able to generate enough power, thanks to its three huge solar panels, each of which is 30 feet (9 meters) long. These arrays will generate about 500 watts of power at Jupiter, mission team members have said.

4. Juno will spin while doing science

Juno spins to stay stable, a strategy that borrows from the design of NASA's old Pioneer probes. Two Pioneer spacecraft (Pioneers 10 and 11) sailed by Jupiter in 1973 and are still cruising out into the solar system, albeit silently; NASA lost contact with Pioneer 10 in 2003 and Pioneer 11 in 1995.

Juno's spin rate has varied quite a bit during its journey so far. When its main engine fires, Juno spins up to 5 revolutions per minute (RPM). During cruise periods, this rate dips to 1 RPM.

When doing science operations, however, Juno will spin at 2 RPM. At this rate, Juno's field of view will move across Jupiter 400 times during one journey from pole to pole. The spacecraft will not use a "scan platform" to point its instruments because of the spinning design, and also because the instruments don't need to point in different directions at the same time.

Juno mission: British rocket engine ready for Jupiter task | Short News

https://youtu.be/N7KluwTxUV8

5. Juno will take nearly three months to reach its final orbit

After Juno inserts itself into Jupiter's orbit, the probe will spend 107 days in what is called a "capture orbit." Scientists chose to take this long way around instead of inserting Juno directly into its final, 14-day orbit, because the direct route would have required a lot of fuel.

The capture orbit not only saves fuel, but it also gives mission scientists a chance to check out their instruments and begin science observations from afar. According to NASA, the team will begin using all the instruments to collect data about 50 hours after Juno is inserted into Jupiter's orbit.

6. Juno has an unusual final orbit

The best way to map any world is to move a spacecraft repeatedly over the poles. Then the entire world can spin beneath the probe, allowing it to map every part of the surface. But at Jupiter, there's a rub — high levels of potentially damaging radiation close to the planet.

As a way to minimize its radiation exposure, Juno will fly in a very elongated orbit. At the south end of its orbit, Juno will be at its closest approach to Jupiter: just 3,100 miles (5,000 kilometers). But as it leaves the south polar region, Juno will fly way out beyond the moon Callisto's orbit, which lies about 1.2 million miles (1.9 million km) from Jupiter.

This highly elliptical orbit will also keep Juno's solar panels in sunlight, NASA officials have said.

NASA's Juno Mission: Everything You Could Want to Know

https://youtu.be/_fI0IrwTMbg

7. Juno will die a dramatic death

In the past few decades, scientists have learned that life is incredibly hardy and persistent. Earth microbes thrive in boiling-hot, deep-sea vents at the bottom of the ocean, and some can even survive exposure to the harsh environment of space.

It's therefore possible that some Earth organisms may still be alive aboard Juno. Scientists and NASA officials don't want to take the chance that such microbes could contaminate Jupiter's ocean-harboring moon Europa — one of the solar system's best bets to host alien life — or other Jovian satellites such as Ganymede or Callisto.

So at the end of its mission, Juno will perform a 5.5-day maneuver that will crash it into Jupiter's atmosphere intentionally. The mission is scheduled to end in February 2018, but it may be extended slightly.

Follow Elizabeth Howell @howellspace, or Space.com @Spacedotcom. We're also on Facebook and Google+. Original article on Space.com.

Mistaken Identity: Ceres' Mysterious Bright Spots Aren't Epsom Salt After All — Strange Ceres: New work suggests that surprising carbonate salts put the shine in the bright spots on the dwarf planet's Occator crater. Researchers also found that Ceres' topography, pictured here, is only consistent with a subsurface less than 30-40 percent ice by volume.
**Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA**

It's a case of mistaken identity: The mysterious bright spots on the surface of the dwarf planet Ceres were thought to be composed of hydrated magnesium sulfate (similar to the magnesium sulfate sold as Epsom salt), but new work reveals a different chemical signature in these bright dots, cooked up in watery conditions beneath its crust.

And the revelations don't end there: Another research paper, also published today (June 29), suggests that Ceres' deep craters and jagged mountain mean the crust is mostly rock, rather than mostly ice as previously proposed.

The dwarf planet, orbiting in the asteroid belt between Mars and Jupiter, seems to bridge the gap between smaller asteroids, rocky planets like Earth and Mars, and the big icy bodies farther out, like the moons of Saturn — its shell is more rocky than icy, but it hosts unexpected chemistry that bears a resemblance to the reactions that develop on Earth, and salts that form in the ultracold conditions of the far solar system. It also hosts the most concentrated surface deposit of the substance sodium carbonate ever seen beyond Earth. [Photos: Dwarf Planet Ceres, the Solar System's Largest Asteroid]

Ceres resides in the asteroid belt, but it dwarfs the other asteroids there at 590 miles (950 kilometers) wide and is an even sphere; it even takes up an estimated third of all the asteroid belt's mass, researchers said. Reserachers believe it could be a planetary embryo — a protoplanet that would have eventually turned into a planet like Earth or Mars under different circumstances. It is the only dwarf planet found closer in than the Kuiper belt, on the solar system's outer edges with Pluto.

The bottom of Ceres' Occator crater shines with bright, reflective patches — the brightest region among those that puzzled and intrigued scientists as the Dawn spacecraft first approached Ceres and then entered orbit in 2015 (after orbiting another asteroid, Vesta, in 2011 and 2012). Eventually 130 bright patches were found on the dwarf planet's dark surface, mostly associated with craters. While researchers first suspected the bright spots might be ice, a closer look revealed they weren't quite that reflective and that they could be composed of salts instead. But the particular salt revealed in this study, published in Nature, by Dawn's Visible and Infrared Mapping Spectrometer would have formed in a process involving liquid water.

"That was something we had not expected," Chris Russell, Dawn's principal investigator and planetary scientist at University of California, Los Angeles, told Space.com. "The carbonates are a very strong indication of the processes now that we believe took place in the interior, that makes it more Earthlike, when it can alter the chemistry inside."

"It's not something that's just lying around out there in space," he added.

Craters like Occator gave the lead author of the Nature Geoscience paper, Michael Bland, something to ponder as well. He calculated that if Ceres' subsurface was more than a certain percentage of ice, it would have a much more "relaxed" appearance, created as the ice warmed over time, instead of the harsh topography actually seen. Rather than a thick layer that's mostly made of ice, the researchers found, the dwarf planet's subsurface must be only 30-40 percent ice, mixed in with rock and a lower-density material, maybe hydrated salts.

**Measurements from Dawn are superimposed on a view of Ceres' Occator crater. The red indicates a high abundance of carbonates in the bright spots found there.**
**Credit: INAF/ASI/NASA/DLR/MPS**

An active world

The composition of the salts found in the crater's bright spots suggests that they formed with the help of liquid water, which would freeze in its pure form but could persist when mixed with salts, which slightly lowers its freezing point. (Water mixed with a different salt is proposed to flow on the surface of Mars.) On Ceres, that water would have emerged from deeper within the dwarf planet, where it could be warmer, or melted at the site of the impact that produced the Occator crater.

"The composition that we found implied that liquid water was present sometime in the recent past of Ceres in the subsurface," Maria Cristina De Sanctis, lead author on the Nature paper and researcher at the Institute for Space Astrophysics and Planetology at the National Institute for Astrophysics in Rome, told Space.com. And the particular salt formed is sodium carbonate, a salt formed from carbon that, on Earth, usually forms as water evaporates from a body of water like a lake or in hot springs. The compounds have been detected off of Earth only in the plumes of material that burst out of Saturn's icy moon Enceladus (they also found ammonia-bearing salts in the mix, also found on Enceladus).

"In the case of Ceres, we have a lot of carbonates — really a huge amount," De Sanctis said. "We did not expect to have such a huge amount of carbonates."

By analyzing the composition of the salts that spot the dwarf planet's surface, De Sanctis said, researchers can learn more about the conditions inside the planet. And a big question is whether liquid water persists below the planet's thick, rocky surface, or whether it was merely present or generated when the crater formed, around 80 million years ago. (Even though the surface layers are not mostly icy, they would have had enough to let the reaction work.)

Strange Ceres

Moving outward in the solar system, objects become colder and wetter, made more of ice than of rock. Ceres is rocky, but the composition of the salts, including ammonia-bearing salts which require super cold conditions to form, has more in common with those outer solar system bodies.

That's a "strange connection" with the outer solar system, Mikhail Zolotov, a researcher at Arizona State University and author of a News & Views article on the new works, which appears in Nature Geoscience, told Space.com.

"The chemistry is unusual, and it's key to understand how the body was formed and how it was evolved," he said.

It raises the question, Zolotov and Russell both said, of whether the material that eventually formed Ceres might have migrated inward from the outer solar system at some point, or whether Ceres formed where it currently orbits.

The story of Ceres' water is far from complete, as well — Russell mentioned that other papers from the Dawn team are in the works that describe how researchers can investigate water on the dwarf planet's surface. "Expect the water story to continue for some period of time, because there's a lot of different ways we can explore water."

Going forward, the researchers said, they will have to check the composition of other bright spots on Ceres to see if the chemical process they've observed is restricted to certain regions or if it's more global. But regardless, the asteroid belt outcast continues to prove a complex, active world.

"The IAU [International Astronomical Union] has defined what a planet is in a particular way," Russell said, "but I think of a planet more as a body which, when it's big enough and has enough activity … is now making things, producing things in its interior that are not just sitting there for the eons but in fact that the body evolves with time inside."

The work in Nature about the bright spots' composition can be found here, and the work in Nature Geoscience about the subsurface composition can be found here.

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