One of the capabilities of the up-coming James Webb Space Telescope
will be to observe exoplanets that transit their stars and to perform
atmospheric characterisation through transmission spectroscopy.
In a recent poll of astronomers, the detection of
"biosignatures" on
exoplanets received the most number of votes for how we are most likely
to detect the first signs of extraterrestrial life.
Now astrophysicist Lisa Kaltenegger and astrophysicist Jackie Faherty,
have
turned that idea on its head.
Doing an analysis of GAIA star astrometry data, which gives positions of
stars and their proper motions in 3D, they iterated time backwards
to try and estimate how many times Earth transited our own Sun
from the perspective of an observer on a planet orbiting a distant
star.
Using stars within 100 parsecs of us, it appears we may have blown
our cover several thousand times.
The tell-tale signs of oxygen in the atmosphere have been detectable for
the past 2.4 billion years but other biosignatures such as the widespread
use of hydrocarbons in industry may have perhaps only been detectable over
the past 260 years.
So whilst we hunt for biosignatures on exoplanets, have we, the hunters,
already become the hunted?
Story in Institute of Electrical and Electronics Engineers (IEEE) Spectrum
Magazine by Michael Dumiak here :-
https://spectrum.ieee.org/tech-talk/...lown-its-cover
