To look for signs of life on distant planets, some scientists have focused on scanning the atmosphere of these planets with the hope of finding signs of oxygen or methane, gases which are mostly tied to life on earth.
The third path has been the search for technologically advanced aliens that are sending radio or other signals out into space, Discovery News reported.
“The fact that we have not found anything means nothing. We have only just begun to search,” Shostak added.
A new e-book from NASA also discusses whether it might be simpler than expected to communicate with aliens, should they ever make contact.
Scientists say communicating with alien life may be similar to using the Rosetta Stone to crack ancient languages.
The Rosetta Stone is a Ptolemaic age granodiorite stele inscribed with a decree issued at Memphis in 196 BCE on behalf of King Ptolemy V.
