The findings showed that scientists can identify gases in the atmosphere of planets lightyears away from Earth, which could eventually allow researchers to find a planet with an atmosphere that could sustain life.
The planet, nicknamed Osiris and known as HD 209458b, is a gas giant 150 lightyears from Earth. It orbits a star similar to the sun, the scientists said.
The findings of the team of scientists, led by Alfred Vidal-Madjar of the Astrophysics Institute of Paris, will be published in the US-based Astrophysical Journal Letters.
Before this latest discovery, Osiris was the first planet known to orbit around a star with an atmosphere and evaporating hydrogen.
Scientists often look for the presence of oxygen in planets when searching for evidence of extraterrestrial life, the scientists said.
"Naturally this sounds exciting -- the possibility of life on Osiris," Vidal-Madjar said. "But it is not a big surprise as oxygen is also present in the giant planets of our Solar System, like Jupiter and Saturn."
The scientists, however, were surprised to discover carbon and oxygen atoms in the upper part of the atmosphere, where the chemicals are broken down into basic elements.
Conversely, in Jupiter and Saturn, carbon and oxygen are in a combined form as methane and water deep in the planets' atmospheres.
Osiris' oxygen and carbon gases appear to blow out of its atmosphere toward space at 35,000 kilometers (21,748 miles) per hour.
"We speculate that even heavier elements such as iron are blown off at this stage as well," said Alain Lecavelier, a team member.
This type of evaporation has led the scientists to believe in the existence of a new class of planets, which they said could soon be discovered by telescopes on Earth and in space.