New data from the European Space Agency's Venus Express mission suggest that Venus was once Earth-like but later evolved in a different way. The findings, published in the journal Nature on Thursday, also confirm that there is lightning on Venus.

"The two planets were, in fact, very similar in the earlier days of the solar system," said Venus Express team scientist Hakan Svendem, "And they have then evolved in different directions, but according to the same rules and explanations." Professor Fred Taylor of the University of Oxford, another scientist on the mission, said "Our new data make it possible to construct a scenario in which Venus started out like the Earth - possibly including a habitable environment, billions of years ago - and then evolved to the state we see now."

Unlike the Earth, Venus lacks a magnetic shield to protect it from the solar wind, a stream of charged particles ejected from the sun. As a result, hydrogen, helium, and oxygen are blown away from the atmosphere on Venus much faster than on Earth. The scientists believe that Venus may once have had liquid water oceans on its surface which, as a result of the solar wind, were largely removed during the first billion years after the formation of the Solar System. "Eventually the oceans boiled off, and all the water ended up as water vapor in the atmosphere," Svedhem said.

Data from the magnetometer instrument on Venus Express confirm that there is lightning on Venus, a once controversial idea. In fact, the findings suggest that lightning is more common on Venus than on Earth.
Unlike the Earth, Venus has undergone runaway greenhouse warming and now has an average surface temperature of 467 degrees Celsius. Some believe that studying how this change came about could lead to insights into how to prevent undesired climate change on Earth. "Understanding the influencing factors of global warming on Venus could help us in mitigating the threat here on Earth," said United Kingdom minister for science and innovation Ian Pearson.

Planets were assembled out of small "building bodies" called planetesimals, which themselves aggregated from the dust in the solar nebula. Planets and satellites are "built-in", and the program comes with some 7500 asteroids and comets. Planets with the perfect blend of molecular constituents orbiting at just the right distance from the sun enjoy what astronomers call a "Goldilocks" orbit. Planets require accretion to form, specifically accretion in aproto planetary disk around a young star. Planets, as we noted, move relative to the stars, and they do so, generally, moving from west to east in the sky.

Mercury

Mercury and Venus are the only planets with no known moons. Mercury, setting, is lost in the trees and glow along the horizon, while Jupiter is off the top of this view. Mercury Mercury is the closest planet to the Sun. Mercury's Moon, 1974Two days before the March 29, 1974, Mariner 10 flyby of Mercury, one instrument began registering bright, extreme ultra violent (UV) emissions that had "no right to be there. Since Mercury has no protective atmosphere, the temperature on the surface ranges from extremely hot on the side facing the Sun to extremely cold on the side that faces away from the Sun. Even then, however, summer temperatures in a mid-latitude location like Erie, Pennsylvania, in the United States would peak around 140 F (60 C) under a Sun that looks twice as large, as Earth moves within even Mercury's orbital path. Second, five of the new planets orbit very near their stars--closer, in fact, than Mercury orbits the sun.

Outer

The outer layers of the Sun exhibit differential rotation: at the equator the surface rotates once every 25. Between the inner and outer planets is an asteroid belt. The planets in our solar system are classified as inner planets and outer planets. On the other hand, atmospheric carbon dioxide condenses at the cold outer edge of the HZ which eliminates its greenhouse warming effect. The outer planets are large gaseous spheres with rings and include Jupiter, Saturn, Uranus, and Neptune. In the solar system's outer region, though, it was chilly enough for ices to remain intact.

Planets are found much more commonly around stars like our sun that are rich in iron and other metals, hinting that such elements played an important role in planet formation. Since all the planets except Pluto orbit the Sun within a few degrees of the plane of the Sun's equator, we know very little about the interplanetary environment outside that plane. While it is still not known precisely how the planets of our solar system were formed, the currently accepted nine planets that orbit around and are illuminated by the sun include Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. Mercury, Venus, Earth, and Mars are the planets closest to the Sun. Each of the planets in the solar system also has at least one additional celestial body, known as a moon that orbits around it while it orbits the sun.

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