The long journey of Galileo ends

2002/04/01 Carton Virto, Eider - Elhuyar Zientzia Iturria: Elhuyar aldizkaria

• Astronautika
• Astronomia

ANDÉN

In the 1970s, when the Pioneer and Voyager ships passed alongside Jupiter, they received interesting but limited data as they could not stop. Then, at NASA they proposed to launch a project to visit Jupiter and its satellites. It was a matter of studying the atmosphere of Jupiter, of checking if the satellite Io had active volcanoes, of studying closely the European icy surface...

Journey of Galileo

Galileo was launched in 1989 by the space shuttle Atlantis. The spacecraft did not have enough energy to direct it to Jupiter and used the momentum of Earth and the gravitational field of Venus. Once he turned around Venus and twice around the Earth, he went to Jupiter. The small amounts of plutonium used to carry out these maneuvers caused the rejection of many people.

Jupiter system studied by Galileo. From top to bottom the moons Io, Europa, Ganímedes and Calisto, and to the left the Great Red Spot of Jupiter. The Great Red Spot is the best-known storm in Jupiter's atmosphere and astronomers have been investigating for nearly 300 years. From north to south is greater than the diameter of the Earth and from east to west is double that of the Earth.

ANDÉN

Surrounding Venus and Earth, he tested the instruments and made the first photographs. The first mistakes also occurred then. The large Galileo antenna was not opened as planned and the entire system had to be reprogrammed to receive all the information through the small antenna.

Galileo's discoveries began before reaching Jupiter. Crossing the asteroid belt between Mars and Jupiter, he discovered the asteroid Gaspra and the small Dactyl satellite of the asteroid Ida. And in 1994 he saw before anyone how the comet Shoemaker Levy was reduced against Jupiter. Astronomers on Earth wait for Jupiter to turn to see the areas of shock.

After a six-year journey, Galileo arrived at the Jupiter system in July 1995, when he released the probe he was bound. Four months after Jupiter's gravitational zone captured the probe, it entered the gaseous giant's atmosphere. Before evaporating, he traveled 135 kilometers of the atmosphere (upper atmosphere of Jupiter) and was receiving data for 59 minutes.

Surprises in the atmosphere of Jupiter

Random deliberately caused the probe to fall into the area known as ‘hot spot’ and scientists to collect data they did not expect, by detecting waters and temperatures much lower than expected. Later, when Galileo made global measurements, they discovered that the atmosphere of Jupiter interspersed wet and dry regions that fell into one of the driest probes.

Photograph taken on June 26, 1996. Scientists have observed in the photos of Galileo structures such as the clusters that cause storms on Earth (the bright white dots of the pictures; the smallest one has tens of kilometers). The probe launched into Jupiter's atmosphere measured winds of 500 km/h and it is believed that thunder heads can be the energy source of the immense wind circulating through Jupiter. In the image you can see the high and dense clouds in white, the tall clouds and fine roses and the low clouds in blue. (Photo: ANDÉN).

Thanks to the data collected by the probe and Galileo, the researchers were able to know some details of the atmosphere of Jupiter. For example, it is divided into three layers: on the outside there are ice cream ammonia clouds, in the center ammonium and hydrogen sulfide crystals and, on the bottom, ice water and perhaps also liquid water.

As for the storms, it was possible to measure the speed of the provoked winds –500 km/h– and determine the causes that lead them. It seems to be due to the increasing vertical circulation of water and the downward movement of the dry wind. And they are super violent. Jupiter's red spot has long been known, but Galileo has found rivals: two white spots that function as a single system. Together they form a storm equal to the diameter of the Earth.

Satellite discovery and discovery

Being a gaseous giant, Jupiter does not have a solid surface like the Earth, but its temperature and pressure inside are very high and, apparently, can have a nucleus of ‘metallic liquid hydrogen’. Hydrogen in this situation, instead of having a gas moving freely, is a special matrix capable of producing huge electric currents.

Photos of Galileo in orbit 9 to Io. Two volcanic peaks can be seen, one at the left boundary of the moon and one at the center. The limit is 140 kilometers high and was detected by Hubble.

ANDÉN

Jupiter has a very powerful magnetic field and this may be due to its special core. Jupiter's magnetic field extends to 975 million kilometers of the planet, beyond the orbit of Saturn, and has served to investigate its satellites. Galileo has mainly studied the satellites Io, Europe, Ganymede and Callisto.

The magnetic field of a body is the reflection of its interior. To understand the internal structure of the satellites, Galileo has analyzed the interaction between Jupiter's magnetic field and satellites. Depending on what crosses the magnetic field will undergo some change. Thus it has been known that Ganymede has its own magnetic field, that there may be liquid water inside Europe, and perhaps also inside Callisto.

By measuring the polarization of light the composition and structure of the surface of the satellites has been studied and the surface temperature has been known by measuring the infrared light emitting. To investigate the interior, in addition to the changes in the magnetic field, they have taken advantage of the Doppler effect. Every time Galileo passed by Jupiter or a satellite, the thrust of gravity made it emerge and on Earth, due to the Doppler effect, the frequency change of the radio signal was measured. Since the thrust of gravity depends on the amount of rock the satellite has, the change of the radio signal allows to know the structure of the satellites.

Repeated mission

Satellite cover Europe. It is believed that under the thick ice surface there may be an ocean of salt water. NASA is preparing the Europa Orbiter mission in the coming years to study Europe.

ANDÉN

Galileo's mission had to last two years, it had to finish its work on December 7, 1997, but due to the proper functioning of the spacecraft and the desire to receive more data, it was agreed to extend the mission for two years. During these two years he closely analyzed European ice, Io volcanoes and Jupiter storms. It was then discovered that under the ice surface of Europe there may be an ocean of salt water.

These discoveries in Europe are the main cause of the destruction of Galileo. NASA is preparing a mission that will study Europe to check if there is liquid water and if it can be alive, but before taking off the Galileo spacecraft was not sterilized, so they do not want to hit Europe.

The accidental impact of spacecraft against the European Moon threatens to produce biological contamination on this satellite, which could crumble the NASA project. The fuel needed to put the Galileo antenna facing the Earth is running out and they want to destroy it under control.

Alleged structure of Io, Europa, Calisto and Ganímedes (starting from above and from the left and turning clockwise). After Galileo's discoveries, scientists change their belief in the interior of Callisto. Unlike the other moons, it was thought that Calisto had no layer, but it seems that the ice and rock layers are somewhat separated. Ganymede seems to have three layers: metallic core, cloak of rock and bark with abundant ice. As for Europe, it has a metallic core that occupies half and a layer of ice about a hundred kilometers thick. Liquid water is considered to be in the stretch. (Photo: ANDÉN).

At the end of the second mission, Galileo approached the satellite Io, the satellite closest to Jupiter. As they feared that Jupiter's violent radiation would destroy the spacecraft's computers, they left it for the end of Io, but radiation was overcome and active volcanoes were found.

Some are warmer than those on Earth, which makes it suspect that silicates rich in magnesium are poured from the surface of Io. The volcanoes of Luna Io were discovered in 1979, and since then they have only surprised. Galileo has approached Io more than ever, detecting data that until now could not be seen.

Thus, NASA decided to expand its mission until 2001 to collect more data from the Io and Europe satellites and investigate how radiation affects a spacecraft near Jupiter. Finally, in September 2003 it enters and is destroyed in the atmosphere of Jupiter.

Last tasks

Before retiring, NASA astronomers have led you to a new visit to the moon volcanoes to take the latest photos. With this last visit they hope to see how some volcanoes have changed in recent years.

In November 2002, by extinction, Jupiter is very close and passes about 500 kilometers from the small satellite Amaltea, inside Jupiter. He will then analyze the mass and density of the Moon, which so far, according to studies, is ten times smaller than Io. Astronomers also expect Galileo to give the key to explaining Jupiter's violent storms and Io's volcanoes before their destruction.

Jupiter satellites analyzed by Galileo and their cover photos. In global images you can distinguish 20 kilometers of structures. They investigate large-scale phenomena such as tectonic and volcanic activity. The central photographs have a resolution 10 times higher and are suitable for the study of regional characteristics. For example, volcanic Io boilers (black spots), cracks in Europe supposedly created by stripes and Calisto holes by the impacts of comets and asteroids. In the photos below you can differentiate structures of 20 meters, so they are used to investigate their composition and physical origin. (Photo: ANDÉN). To see the photo well go to the pdf.