Six close encounters with Jupiter reveal the mystery of the Great Red Spot that has existed for more than 350 years

On a clear night, you can often see a very bright star, which is Jupiter. This bright star, visible to the naked eye, has appeared in the records of various cultures since ancient times. In ancient Babylonian culture, it represented their god Marduk, the Romans named it after the god Jupiter, and in China, it is called Jupiter.

Jupiter is the largest and fastest rotating planet among the eight planets in the solar system. It is also the heaviest planet in the solar system, with a mass that is one thousandth of the sun and 2.5 times the mass of the other seven planets combined. So far, in addition to the Jupiter Icy Moon Probe, a total of six human probes have flown to this giant gas planet. Let's take a look at who they are.

Pioneer Series Detectors

"Pioneer 10" and "Pioneer 11" were the first two probes to fly to Jupiter. They both belonged to the United States' unmanned planetary exploration mission "Pioneer Program", whose main mission was to explore the solar system beyond the asteroid belt.

On March 3, 1972, the Pioneer 10 probe was launched. It created many firsts. It was the first spacecraft to successfully cross the asteroid belt and the first to observe Jupiter at close range. On December 3, 1973, it sent back the first set of close-up images of Jupiter. Pioneer 10's exploration of Jupiter lasted for 2 months, sending back about 500 photos of Jupiter and its satellites, with the highest resolution of about 320 kilometers, clearly showing the characteristics of Jupiter's atmosphere such as the Great Red Spot, revealing unprecedented details of Jupiter. It also detected that the radiation intensity around Jupiter is 10,000 times that around the Earth.

Artist's impression of the Pioneer 10 probe

On April 6, 1973, the Pioneer 11 probe was launched. Due to the great success of the previous Pioneer 10, scientists assigned Pioneer 11 a more difficult task - to explore Saturn. It used Jupiter's strong gravity to change its orbit and fly towards Saturn. Although its main task was not to explore Jupiter, it obtained clearer images of Jupiter at a closer distance, obtained detailed images of Jupiter's Great Red Spot, obtained images of Jupiter's poles for the first time, and measured the mass of Callisto. Its exploration of Jupiter further deepened mankind's understanding of Jupiter.

Voyager series probes

Following the Pioneers, two more probes flew to the outer solar system. They were Voyager 1 and Voyager 2. These two probes still had the outer solar system as their main mission, but they flew farther. Both probes used plutonium batteries to provide long-term energy for their long journeys in space.

Voyager 1 flies over Jupiter's Great Red Spot

Voyager 2 was launched first on August 20, 1977. It is the only probe that has visited the four gas giants - Jupiter, Saturn, Uranus and Neptune. Subsequently, Voyager 1 was launched on September 5, 1977. The two probes once again opened the door to a new world for scientists. They found that Jupiter's famous Great Red Spot is a complex storm system rotating in a counterclockwise direction, and also found some small storms and vortices. Moreover, Jupiter has rings like Saturn, but they are much darker than Saturn. The outer side of the ring is 129,000 kilometers away from the center of Jupiter, and the inner side is 30,000 kilometers away from the center of Jupiter.

In addition, the two probes also made many discoveries on Jupiter's four satellites. They discovered active volcanoes on Io, which was the first time that humans discovered active volcanic activity on other planets in the solar system. A total of nine volcanic eruptions were observed on Io, and the eruptions of volcanic eruptions could reach as high as 300 kilometers. The photos of Europa taken by Voyager 2 allowed scientists to preliminarily infer that there is an ice shell on the surface of Europa, and an ocean about 50 kilometers deep is hidden underneath. It also discovered two obvious landforms on Ganymede: pits and deep trenches. Scientists speculate that Ganymede's ice shell is undergoing violent crustal movement. On Callisto, a large number of traces of ancient craters were found, but these traces have become very shallow due to the passage of time and crustal changes.

These two flight missions also discovered Jupiter's three small satellites, Io, Io and Io, and captured the aurora on the back of Jupiter.

Galileo Jupiter Orbiter

On October 18, 1989, the Galileo Jupiter probe was launched from the Atlantis space shuttle. It was the first spacecraft dedicated to exploring Jupiter and one of the most successful probes launched by NASA.

Galileo Jupiter probe

The Galileo probe cost nearly $1 billion and is the most sophisticated interstellar spacecraft ever built by the United States. The entire launch plan cost about $1.5 billion. The probe weighs 2,550 kilograms, uses a nuclear power plant, and contains 22.7 kilograms of radioactive uranium-238. The probe is equipped with 17 scientific instruments, including cameras, near-infrared survey spectrometers, magnetometers, cloud meters, and atmospheric structure meters, which are used to survey and study the composition of Jupiter's atmosphere, cloud structure, temperature, and magnetic field.

In July 1995, the orbiter released an atmospheric probe to Jupiter and continued to fly along Jupiter's orbit. The Galileo Jupiter probe was originally scheduled to have a mission of about 2 years, but it actually flew in space for nearly 14 years. In the more than 7 years since it arrived in orbit around Jupiter, it has greatly refreshed the observation record of Jupiter, sent back 30,000 megabits of data including 14,000 photos, found evidence of underground liquid salt water on Jupiter's three satellites, conducted the first complete survey of the Jupiter system from orbit, and made the first direct measurement of Jupiter's atmosphere. Its greatest contribution was taking photos of water on Europa, which made scientists more certain of the previous speculation that there was an ocean on Europa.

On September 21, 2003, Galileo flew to the back of Jupiter and "jumped" into Jupiter's atmosphere at a speed of about 170,000 kilometers per hour, ending its 14-year space journey in a nearly suicidal way. There was a reason for this heroic jump. NASA originally planned to keep Galileo in Jupiter's orbit, but its discovery of the possible existence of an ocean on Europa changed the experts' minds. Since Galileo was not sterilized during its design, it might collide with Europa when its fuel was about to run out. Once it hit Europa, it might bring Earth's microorganisms to Europa, which would affect the subsequent search for native life on Europa, so "jumping" into Jupiter's atmosphere was the best choice.

Galileo also made a great contribution to the study of Jupiter's satellites. Before Galileo arrived at Jupiter, people had discovered a total of 16 satellites of Jupiter. After Galileo arrived, more satellites were discovered. Now this number has risen to 92.

It is worth mentioning that on its way to Jupiter, Galileo filmed a movie of the Earth's movement in space, took high-resolution photos of two asteroids, and captured the spectacular scene of a comet hitting Jupiter in 1993.

Juno Jupiter Probe

The Juno probe is the second exploration project of NASA's "New Frontiers" program. On August 5, 2011, the Juno probe began its journey to Jupiter. On July 4, 2016, Juno entered Jupiter's orbit. It became the first spacecraft to penetrate Jupiter's dense clouds, and aims to investigate the existence of icy cores on Jupiter; determine the amount of water on Jupiter; the amount of ammonia in the atmosphere; study the convection of Jupiter's atmosphere, and explore Jupiter's magnetic field, gravitational field and polar magnetosphere.

Juno probe flies by Jupiter

At 2 p.m. on January 13, 2016, Juno broke the record for the farthest voyage of a human probe relying on solar energy. At that time, it was about 793 million kilometers away from the sun, while the distance from the earth to the sun is only about 150 million kilometers.

On July 11, 2017, the Juno probe passed the perigee and officially flew over Jupiter's Great Red Spot. A NASA spokesperson said: "This will be the first time that humans have observed this huge storm up close. This storm has been discovered by humans since 1830, and it may have existed for more than 350 years."

Juno carries three huge solar panels, each 2.7 meters wide and 10 meters long, which is about the size of a tractor trailer. These three solar panels can provide 14 kilowatts of electricity, but after entering Jupiter's orbit, the power provided is only 400 watts, which can only light up a few light bulbs. Therefore, the scientific instruments and computers on Juno are highly energy-efficient, and the research team has also carefully designed the orbit around Jupiter for Juno to receive as much sunlight as possible.

According to the original plan, the Juno probe will travel a total distance of more than 716 million kilometers, and will orbit Jupiter 33 times in one Earth year. In 2018, Juno will end its mission and crash into Jupiter's atmosphere. But over-service seems to have become a routine for American space probes. At present, Juno has not yet ended its space journey and is still sending back precious observation data.

The name of this probe is quite interesting. In Roman mythology, Juno is the wife of the god Jupiter. Jupiter used his magic power to cover himself with clouds, but Juno could see through the clouds and understand Jupiter's true face. Therefore, the probe was named after it, hoping that it could reveal the secrets hidden in this gas giant planet shrouded in clouds and mist.