A first look at Jupiter through the eyes of Juno
As NASA’s Kepler spacecraft has taught us, finding planets around other stars is not uncommon – it is actually expected. However, what continues to puzzle scientists to this day is how the Solar System formed with terrestrial planets closest to the Sun and icy gas giants farther away, separated by an asteroid belt of planetary debris.
Nevertheless, over the years and, in part, due to a selection effect of the “transit” method of planet detection, it has been more common to find Jupiter-like planets closer to their stars than Mercury is to the Sun. This poses the question: how did Jupiter end up so far away from the Sun, but other Jupiter-like planets so close to their stars?
The answer to this question will allow scientists to gain a better understanding of the formation and evolution of solar systems such as our own. Therefore, in order to study Jupiter in more depth, NASA and the Southwest Research Institute (SwRI) launched the Juno spacecraft in August 2011. Juno was sent to study four main areas of interest about Jupiter: origin, interior, atmosphere, and magnetosphere.
To investigate the planet’s origin, Juno will determine the water abundance in Jupiter’s atmosphere. The purpose of studying its interior is to map the gravity and magnetic fields of the gas giant, since Jupiter boasts the largest magnetic field in the Solar System. Juno also looks at Jupiter’s atmosphere and magnetosphere to study its aurorae and chemical compositions.
As of August 27, Juno had safely arrived at Jupiter, assuming its initial 53-day polar orbit while making its first closest approach. A polar orbit allowed for the August 27 observation of Jupiter’s aurorae. With evidence of the structure being influenced by the moons Io, Europa, and Ganymede, Juno provided a new perspective of the phenomenon until recently only observed from Earth-based telescopes.
“Nothing about the aurora[e] was as expected,” said Scott Bolton, associate vice president of R&D at SwRI, as he spoke to the curious listeners at the Division for Planetary Sciences meeting in Pasadena, California, on October 19.
Juno discovered that the magnetic field of Jupiter closely resembles models developed by scientists prior to any in-situ measurements. However, where the model diverges is where Juno will provide the required information to understand the most complex structures during future orbits. The instruments studying the gravity fields, however, showed that scientists’ initial models of those were inaccurate.
The gravity field of Jupiter is full of “guarded secrets”, says Bolton. The highlight of the data from the August 27 flyby of Juno looked into Jupiter’s atmosphere, showing the structure below the surface. The observation demonstrates that the belts clearly outlined on Jupiter’s outer atmosphere are seen at depths up to around 350 to 400 km. This indicates that the belts of Jupiter are evolving and present under the outer atmosphere, giving scientists hints about the wind patterns and chemistry of the upper atmosphere.
The first impressions from Jupiter set it apart from its gas giant neighbor Saturn. There are no apparent structures in Jupiter’s atmosphere like the hexagonal wind pattern that Saturn boasts at its north pole. Jupiter, however, has a newly detected cyclone at its north pole. Roughly 7,000 km across and 85 km in height, this half-Earth-sized storm is just visible where the Sun terminates and the dark side of Jupiter begins. With its complex features and structures, Jupiter is unlike any other gas giant in the Solar System.
Juno was scheduled to descend into a 14-day orbit shortly after its arrival. However, due to a sticky valve in its main engine, the spacecraft entered safe mode at 05:47 UTC on October 19, 2016. It remained in the larger 53-day orbit until engineers had determined that it was safe to boost the spacecraft closer to the planet. Staying in its larger orbit around Jupiter would not have diminished the value of the mission; it only extends the time between obtaining the flyby data that is most desirable.
Nevertheless, on Monday, Oct. 24, engineers commanded Juno to exit safe mode, and confirmation of the safe mode exit was received back on Earth at 17:05 UTC. On Tuesday, Oct.25, at 18:51 UTC, the spacecraft successfully conducted a minor burn of its thruster engines to prepare for its close flyby of Jupiter. The mission team is still investigating the anomaly in the two main engine check valves that had caused the onboard computer system to reboot.
In order to keep people interested and involved with the Juno mission, SwRI created a website where people can vote on locations they want the cameras of Juno to be pointed. There are even images available that were processed by amateur astronomers along with the science team at SwRI. Juno will continue to send back new data every 53 days until it descends into Jupiter at the end of its mission, currently scheduled for early 2018.
Mackenzie Kane is currently working towards receiving her Bachelors degree in Planetary Sciences and Physics at the Florida Institute of Technology. For the past several years, Kane's area of active research has been with NASA's Kepler Space Telescope mission and its search for extrasolar planets. Kane has a deep love of learning about the mysteries that space holds through the ever-growing technology that is launched into orbit. My goal upon graduation is to continue writing about the exciting research and technology furthering our presence in space and delivering it to the public in easily accessible ways. Kane was accepted as the second intern from Florida Tech to write for SpaceFlight Insider and our outlet will now work to provide her with access and experience.