For nearly two years, the NASA Juno automatic interplanetary station has been in orbit with the giant planet Jupiter. Despite the technical problems, the station collected a lot of interesting data, picked up an abundance of colorful photos and was very close to the goals of its research - to find out what is hidden in the cloudy interior of the largest planet in the solar system.
Juno (Juno - the wife of Jupiter in Roman mythology, the back-face of the Jupiter Near-polar Orbiter) arrived at the giant planet in June 2016. Since then, it has rotated around the planet in a highly elongated elliptical orbit, which allows it to fly over the poles of the planet. Juno is the second artificial satellite of Jupiter, the first - Galilleo flew in the equatorial plane and studied natural satellites.
Thanks to a new orbit, allowing close encounters and inspection from afar, Juno gets unique information. A set of scientific instruments designed to study the gas interior of the planet. It includes ultraviolet and infrared spectrometers, microwave radar, detectors of cosmic particles and plasma. The magnetometer is designed to study the powerful magnetic field of the planet, and the color camera - to capture the upper atmosphere. With the help of a radio complex for communication with the Earth, the gravitational field of the planet is studied, which affects the speed of the spacecraft.
What an infrared spectrometer sees Unlike most distant space stations, Juno is equipped with solar panels, spread over an enormous area of 64 sq m. At a distance of Jupiter, the energy input from the Sun is about 4% of the Earth’s level, therefore Juno solar panels produce about as much energy as an ordinary earthly solar battery for giving an area of 3 square meters. This decision was forced, because NASA ran out of plutonium-238, which was used for
radioisotope thermoelectric generators . The last isotope reserves, bought in Russia in the 90s, travel across Mars as part of the Curiosity rover, and fly to the outer limits of the Solar System in the New Horizons probe. Now NASA has resumed production of plutonium-238, but temporarily switched to solar energy.
Juno is in an extended orbit around Jupiter, the closest point of flight above the cloudy layer of the giant planet is at an altitude of 4200 km, and the furthest is at a distance of 8 million km. The station flies over a full flight in 53.5 Earth days. A preliminary flight plan suggested reducing the ellipse of the orbit, to a distance of 4,200 km to 3 million km. The plan had to be changed when Juno ran into technical problems. Two valves stuck on helium fuel tank pressurized tanks. The engine could not perform a maneuver of braking and lowering the orbit, so we had to stay on the transition. Thanks to the new orbit, the mission can be extended; it has less impact on the radiation belts of the planet, and on-board electronics with scientific instruments will last longer. In the summer of 2018, scientists will consider the possibility of extending the scientific activities of Juno.
From the summer of 2016 until May 2018, Juno made twelve revolutions in her orbit and was able to transmit new data on the distribution of the atmospheric layers of the planet, penetrate under the cloud cover of Jupiter’s poles, discover the new radiation belt and find out about the unexpected connection of the giant's depth with its magnetic field. Everyone has access to the
archive of images of the Juno color camera, and enthusiasts independently process them, creating real art canvases. Examples of such works can be found on the authors' channels:
Björn Jónsson ,
Seán Doran ,
Roman Tkachenko .
The most spectacular pictures of typhoons in the infrared range turned out at the pole of Jupiter. One central polar typhoon of the planet is surrounded by eight other stable typhoons, moreover, they are poorly noticeable when viewed “with the naked eye”, and are at depth.
Jupiter is not the only planet in the solar system with permanent atmospheric structures at the pole. Venus has a couple of typhoons, which is also considered on a cloudy depth in the infrared. The Saturn pole decorates a regular hexagon, and although the reasons for its occurrence are not precisely established, the possibility of six typhoons forming around one central one has been experimentally
confirmed .
Jupiter brought surprises at the more studied equator. It turned out that the light equatorial band is a stream of ammonia that rises from a deeper layer.
Previously it was believed that the upper atmosphere of the giant planet to a depth of 100 km is homogeneous, but now it is clear that this is not the case.
The origin of brown and orange hues in the atmosphere is still unknown, according to one of the hypotheses - these are hydrocarbons that change their color under the influence of the solar ultraviolet. Another possible compound is ammonium hydrosulfide, a yellowish salt based on nitrogen, sulfur and hydrogen. White clouds are ammonia crystals. The speed of movement of oncoming wind flows reaches 360 km / h.
Jupiter's famous Red Spot is a large typhoon that occurs at the junction of oncoming atmospheric flows in the southern hemisphere. Typhoon rises eight kilometers above the surrounding clouds, and goes into the bowels of the planet. The red spot has about 16 thousand kilometers in diameter, i.e. larger than the diameter of the Earth, it has been observed for almost 200 years, and during this time has reduced its size by half, gradually decreasing today. Along the edge of the Red Spot, winds blow at speeds of up to 430 km / h, but the movement inside is slower. The causes of the long-term stability of the Great Red Spot of Jupiter are not known, perhaps it is somehow connected with the heterogeneity of the magnetic field of the planet.
The magnetic field of Jupiter is more complicated in the northern hemisphere of the planet, where between the equator and the pole there is a vast area of high magnetic field strength, which falls to the north pole. South of the equator, the magnetic field also has irregularities, including in the region of the Red Spot. It is believed that the magnetic field arises from currents flowing in the outer core of Jupiter, consisting of liquid “metallic” hydrogen, which is formed under high pressure at a depth below 15 thousand km.
The magnetic field of the giant planet, interacting with the solar wind, as well as plasma and charged particles emitted from natural satellites, forms powerful radiation belts. The Earth’s radiation belts are replenished mainly from the Sun, while in Jupiter, the main source of ionizing radiation is the emission of gases from Io and other large satellites: Europe, Ganymede, Callisto. Io is located closest to Jupiter and is the most volcanically active body in the solar system: dozens of volcanoes constantly erupt there, and Juno was able to see them in the infrared.
While flying close to the cloudy surface of the planet, Juno was able to clarify the characteristics of the radiation belts, and even discover a new one. The three moons of Jupiter rotate inside the radiation belts, which pose a threat to electronics and future space explorers. Electrons and heavy charged particles: protons, ions of various gases, possessing high energy and speed rotate around the giant planet at distances up to 1 million km. It turned out that at a close distance from the planet in the equatorial plane there is a radiation belt filled with hydrogen ions, oxygen and sulfur, which move at speeds close to the speed of light. Closer to the poles, a meeting was expected with elements of a radiation belt filled with light and fast electrons. But even there Juno registered the presence of heavy charged particles that create a lot of noise in the devices.
Although Jupiter is a gas giant and does not have a solid surface, it is far from all filled with cloudy typhoons. The so-called “weather layer” of Jupiter, which demonstrates the effects of atmospheric dynamics, extends inland for about 3 thousand km. Further, high pressure and temperature turn the main component of the atmosphere of the giant planet - hydrogen into an electrically conductive liquid. Due to the electrical conductivity, the liquid “ocean” of Jupiter falls into dependence on the powerful magnetic field of the planet, and the wind of the “weather layer” no longer has power over it. Deeper than 3 thousand km, the planet behaves like a solid body, which was
established by analyzing the gravitational field. It is assumed that Saturn's cloudy “weather layer” should be even thicker, while brown dwarfs, which are also related to Jupiter, should be thinner.
The study of Jupiter continues. All the data accumulated by Juno have not yet been processed, and the mission of the apparatus can be extended for a year or more, so new discoveries, clues and new secrets from the depths of the largest planet of the solar system are ahead.