Original sentence: It is unknown whether any such life exists or ever existed in the past, although many scientists think it likely that on Mars, for instance, life either exists or has existed.Various claims have been made for evidence of extraterrestrial life, such as those listed in a 2006 New Scientist article, which the magazine describes as "hints" rather than proof
Edited sentence: However, the mainstream scientific community regards all such claims as unconvincing.It is unknown whether any such life exists, and all discussion of it must be regarded as highly speculative.Various claims have been made for evidence of its existence, such as those listed in a 2006 New Scientist article, which the magazine describes as "hints" rather than proof