Known as 55 Cancri e, the super-Earth is among several rocky planets outside our solar system with a significant atmosphere, enveloped in a blanket of carbon dioxide and carbon monoxide.
The exact amounts are uncertain. Earth's atmosphere is a mixture of nitrogen, oxygen, argon and other gases.
"This is probably the most solid evidence yet that this planet has an atmosphere," said Ian Crossfield, an astronomer at the University of Kansas who studies exoplanets.
Super-Earth refers to the size of a planet; 55 Cancri e is larger than Earth but smaller than Neptune.
Boiling temperatures on this planet can reach up to 2,300 degrees Celsius, which means it is unlikely to be home to life.
Instead, scientists say the discovery is a promising sign that there may exist other rocky planets with thick atmospheres that could be more hospitable.
The exoplanet, 41 light-years away, is eight times heavier than Earth and its surface is covered with oceans of magma.
The research was published in the journal Nature.
