Earth and Venus are nearly the same size.
extraterrestrial...? wait, sorry, it's 'inferior planets'.
Earths twin is venus!
I think you mean extrasolar planets. Technically, all planets except Earth are "extraterrestrial." At last report there were almost 900 of them, with more to follow. They aren't a "group" in the usual sense, just a category.
Extraterrestrial are unknown humans. They are humans, but different kinds from different planets. Like aliens and UFOs. The scientific community think this is true. They think they come from planets beyond Earth...
They search for extraterrestrial life on other planets.
At this time we have no evidence of any extraterrestrial life.
Extraterrestrial life is defined as life that does not originate from Earth. Life on other planets is a simpler way to word it. Aliens on other planets is an example (but I doubt aliens live on other planets) of extraterrestrial life. Also, bacteria are another example. There is proof that there was once water on Mars, and that there may have been bacteria living in that water. That bacteria would also be considered as extraterrestrial.
This field is called "exobiology".
Nope. Unless exobiology is correct, in which case we're all extraterrestrial. no
An astrobiologist.
Yes, Earth is confirmed to have both water and life (though not extraterrestrial life). As for the other 7 planets, no life has been found as of 2017, and only Mars has evidence of water, though this information could change in the future.
It is still called life it is just called extraterrestrial life