Ancient astronomers saw faint points of light that seemed to move among the stars. These objects were called planets, and each one of them was given the name of a god. In the 16th and 17th centuries, scientists came to recognize that the planets were physical bodies that revolved around the Sun. However, it was only recently, in the late 20th century, that technological advances permitted the direct study and the magnificent close-up photographs of the planets in the solar system.
From the sightings by Galileo to the construction of space stations capable of sheltering humans, interest in revealing the mysteries of the planets has never ceased. Detailed studies of the rings of Saturn, the patches of ice at the poles of Mars, the exploration of various comets and asteroids, and the flybys of the great moons of the major planets are among the most striking results of space exploration to date.
Mars in the Sights
There was a time when it was thought that Mars, our closest neighbor, harbored life. Perhaps for this reason it is the planet that has been most explored by various spacecraft from the decade of the 1960s onward, and it is therefore the one we know the best, apart from the Earth. Mariner 9 in 1971 and Vikings 1 and 2 in 1976 revealed the existence of valleys and immense volcanic mountains. In 2001 the
launched the Mars Odyssey mission, which indicated that liquid water exists at great depths. United States
Named after 2001: A Space Odyssey, the probe was launched by NASA from
Cape Canaveral on April 7, 2001. It entered into Martian orbit in October of the same year. The Mars Odyssey was designed for a number of functions, such as taking images in the visible and infrared spectrum, studying the chemical composition of the planet's surface, and investigating the existence of possible sources of heat. One of its purposes was also to find traces of hydrogen and thus water on Mars. Finally, the Mars Odyssey was used in support tasks for other Mars missions, acting as a radio-signal repeater between Earth and probes on the Martian surface.
Jupiter in Focus
The fifth planet of the solar system was visited by Pioneer 1 and 2, Voyager 1 and 2, and Cassini. However, the most significant visitor was Galileo, launched by NASA on
Oct. 18, 1989. Galileo consisted of an orbiter and an atmospheric probe. After a long voyage, the atmospheric probe penetrated some 125 miles (200 km) into the atmosphere of Jupiter on Dec. 7, 1995, transmitting data about the atmosphere's chemical composition and Jupiter's meteorological activity. The orbiter continued sending information until it crashed into the gaseous giant on Sept. 21, 2003.
Galileo was designed to study the atmosphere of Jupiter, its satellites, and the magnetosphere of the planet. To get there, it did not use a direct path but had to perform an assisted trajectory, passing by Venus on
Feb. 10, 1990. Then it flew by the Earth twice and arrived at Jupiter on Dec. 7, 1995. The probe succeeded in sending information of unprecedented quality with a low-gain antenna about the satellites of Jupiter, its moon Europa, and various examples of volcanic activity in its moon Io. It also contributed to the discovery of 21 new satellites around Jupiter. The mission was deactivated in 2003, and the vehicle was sent to crash into the planet. The purpose of this termination was to avoid future collision with its moon Europa that might have contaminated its ice; scientists believe that extraterrestrial microscopic life may have evolved on Europa.
A View of Saturn
The longedΩfor return to Saturn was the result of a scientific alliance between NASA and the European Space Agency (ESA). On
Oct. 15, 1997, after a number of years of development, the fruit of this collaboration lifted off toward this enormous gas giant. The mission of Cassini, the mother ship, was the exploration of Saturn. It carried a smaller probe, Huygens that was to land on Saturn's largest moon, Titan, and transmits images and sounds from the surface. The Huygens probe accomplished this prodigious feat, demonstrating once again the capacity of humans to respond to the challenge of frontiers.
The trajectory of Cassini-Huygens was long and complicated, because it included strategic flybys of Venus (1998 and 1999), Earth (1999), and Jupiter (2000). Each one of these encounters was used to increase the craft's velocity and to send the spacecraft in the appropriate direction (a maneuver known as a gravity assist). Finally, and after almost seven years, traveling some 2.2 billion miles (3.5 billion km), the spacecraft arrived at its destination. It brought an end to the long wait since the last visit of a probe to Saturn—the 1981 flyby by Voyager 2.
Toward Venus and Pluto
The New Horizons mission, launched by NASA in January 2006, is a voyage that will carry the spacecraft to the limits of the solar system and beyond. The most important goal of the voyage is to visit Pluto, a dwarf planet (a designation made in 2006 by the International Astronomical Union). The ship flew past Jupiter to gain enough speed to get to Pluto in the year 2015. It will have six months to make observations of Pluto, after which it will continue its voyage toward the region of the solar system known as the Kuiper belt.
An unmanned space mission by NASA whose destination is to explore Pluto and the Kuiper belt. The probe was launched from
Cape Canaveral on Jan. 19, 2006. It flew past Jupiter in February 2007 to take advantage of the planet's gravity and increase its speed. It will arrive at Pluto on July 14, 2015. Finally, the probe will fly by one or more objects in the Kuiper belt. The principal objectives of the mission are to study the form and structure of Pluto and its satellite Charon, analyze the variability of the temperature on Pluto's surface, look for additional satellites around Pluto, and obtain high-resolution images. The power source for the spacecraft is a radioisotope thermoelectric generator.
The Venus Express
Venus is a little smaller than the Earth and has a dense atmosphere. Because it is located at slightly more than 67 million miles (108 million km) from the Sun, it receives almost twice the solar energy as the surface of the Earth. The
Venus Express is the first mission of the European Space Agency to Venus. The scientific aims include studying in detail the atmosphere, the plasma medium, the surface of the planet, and surface-atmosphere interactions. It was launched from the Baikonur cosmodrome on
Nov. 9, 2005. The mission will last two Venus days, some 500 terrestrial days. The spacecraft entered into orbit on April 11, 2006.
Closer to the Sun
The space probe Ulysses was launched from the space shuttle on
Oct. 6, 1990. It completed its first orbit around the Sun in 1997 and since then has carried out one of the most in-depth studies ever about our star. The probe's orbits allow it to study the heliosphere at all latitudes, from the equator to the poles, in both the northern and southern hemispheres of the Sun. The joint NASA and ESA mission is the first to orbit around the poles of the Sun. It orbits the Sun at 10 miles per second (15.4 km/s).-
- Surya Chaitanya
- Surya Chaitanya