NASA's Juno probe observations have updated people's understanding of the amount of water in Jupiter's atmosphere
Illustration: Images taken by Juno's imager in the southern part of Jupiter's equator, where Jupiter's poles are not shown on the left and right sides of the picture. The photo was taken on September 1, 2017. Source: Original text.
Not long ago, NASA's Juno task force published its first scientific conclusion on the amount of water in Jupiter's atmosphere in the journal Nature Astronomy, which showed that the number of water molecules in Jupiter's atmosphere near the equator accounts for about 0.25% of the total molecular number, which is almost three times that of the Sun. Since the Galileo probe arrived on Jupiter, it has been thought that Jupiter's water content may be extremely small (compared to the Sun, but not directly compared to the content of liquid water, but to hydrogen and oxygen), but this new conclusion for the first time broke the understanding that these gas giants may be rich in water.
Accurately estimating the amount of water in Jupiter's atmosphere has been a long-cherished wish of planetary scientists for decades, because the number hidden in the gas giant is the final piece of the puzzle to solve the mystery of the formation of the solar system. Jupiter is likely to be one of the first planets in the solar system to form, absorbing most of the material that is not absorbed by the sun, including gas and dust.
Illustration: Portrait of the Juno probe. Source: NASA.
Figuring out Jupiter's water content is not only an important step in studying the formation of Jupiter and the solar system, but also necessary for studying Jupiter's meteorological processes (how the winds on Jupiter blow) and its internal structure. Although Voyager and a number of other probes have observed lightning in Jupiter's atmosphere, which vaguely reveals that Jupiter's atmosphere may contain enough water (because lightning usually only occurs in humid environments), there is still no way to estimate its exact content.
In December 1995, the Galileo probe[1] opened its parachute and landed slowly after penetrating Jupiter's atmosphere, sending exploration data to Earth and holding out for 57 minutes before it was destroyed. As it descended 75 miles (120 kilometers), ambient pressure rose to about 320 pounds per square inch (22 kPa), and its spectrometer measured the amount of water in Jupiter's atmosphere. When this data was sent back to Earth for scientists to see, everyone was shocked, because the value was ten times less than expected.
Illustration: Schematic of Juno measuring data over the Great Red Spot and transmitting it back to Earth. Image source: SwRI.
Even more surprising is that in the deepest places where Galileo is still able to transmit data back, measurements of atmospheric water content still seem to have a tendency to rise with increasing depth. It is reasonable to say that the atmospheric composition of this place should already be evenly mixed, so the content of water components should not change, and should be quite close to the average of local or even the entire atmosphere of water content. There are indications that Galileo's bad luck landed on Jupiter in a particularly water-scarce and warm place, and this assertion is supported by infrared imaging results from ground-based telescopes.
Illustration: Infrared and visible images of Jupiter. Source: NASA.
Water content is measured at high altitudes
Launched in 2011, juno is a solar probe that rotates in space. With Galileo's experience, the probe's purpose was to measure the water content of the atmosphere in different regions of jupiter, a giant planet. Juno's microwave radiometer (MWR) is a new type of planetary high-altitude detection instrument that simultaneously uses the sensing signals of six antennas to measure the temperature of the atmosphere at multiple depths at high altitudes above Jupiter. The microwave radiometer works on the principle that water molecules absorb microwaves of a specific wavelength, the same principle as a microwave oven to heat food quickly. After the water molecules in Jupiter's deep atmosphere are warmed up by absorbing microwave radiation and the ammonia molecules (the two molecules can absorb microwave wavelengths of similar length), people can measure the temperature to guess their content in the atmosphere.
Juno collected a lot of this data during its first eight flybys over Jupiter and transmitted it back to Earth for the science team to study. Initially, the observation area was chosen near the equator because the atmosphere here appears to be more uniform than elsewhere, even at deeper levels. Juno was able to measure the depths of Jupiter's atmosphere in the sky with its microwave radiometer, even deeper than Galileo— it could detect atmospheric data at depths of 93 miles (150 kilometers), where air pressures can reach about 480 pounds per square inch (33 kPa).
"We found that the water content of the equatorial atmosphere is much higher than the data given by Galileo." Li Cheng, a scientist at the University of California, Berkeley and a participant in the Juno project, said, "After all, Jupiter's equatorial region is a special region, we still need to compare these data with the atmospheric moisture content of other parts of Jupiter to see if it will be different." ”
Illustration: Photo of Jupiter's equatorial region. It can be seen that jupiter has a thick layer of white clouds above the equator, but these clouds are transparent to microwaves, so Juno's microwave radiometer can detect water levels deep in Jupiter's atmosphere. The photo was taken by the Juno on December 16, 2017. Source: Original text.
Juno's "North Drift" plan
Juno's orbit around Jupiter took 53 days, and now its orbit is slowly moving northward according to a predetermined schedule, and each time it flies by Jupiter, it can make more areas of Jupiter's northern hemisphere more clearly visible to people. Scientists on Earth are also waiting for more data from Juno, eager to understand how the amount of water in Jupiter's atmosphere changes with latitude and region. In addition, jupiter's polar regions have many cyclonic storms,[3] and by analyzing these storms, scientists can also derive a lot of information about the overall water abundance of Jupiter, a gas giant.
Juno flew by Jupiter on February 17, 2020, marking its 24th flyby. Its next flyby of Jupiter will be on April 10, 2020.
Illustration: Schematic of the Juno orbit. Source: NASA.
"Every time Jupiter juno makes many big discoveries." Bolton said, "We can discover something new about Jupiter every time." Juno tells us something important: we'll have to get closer to Jupiter to test the validity of existing theories. ”
The Juno mission was managed by NASA's Jet Propulsion Laboratory in Pasadena, California, on behalf of Lead Researcher Scott Bolton of the Southwest Research Institute in San Antonio. The mission is also part of NASA's New Frontiers Program, which is managed by NASA's Marshall Space Flight Center in Huntsville, Alabama, on behalf of NASA's Science Mission Directorate. The Italian space agency provided the Jovian Infrared Auroral Mapper and the Ka-band transponder. Lockheed Martin (based in Denver) built the spacecraft itself and was responsible for the operations.
BY: Tony Greicius
FY: The Romantic School
If there is any infringement of the relevant content, please contact the author to delete it after the work is published
Please also obtain authorization to reprint, and pay attention to maintaining completeness and indicating source