In Situ and Remote Sensing for Life
Pp. 179-198 (20)
In this chapter we discuss the several attempts to search for life in the universe.
Parts of this chapter are extracted from chapter 10 of another book of the author . The
Drake equation which estimates the probability for extraterrestrial civilizations being on the
same technological level as we is discussed and approvements are suggested.
• Active search: this comprises in situ measurements. Several objects, like Venus, Mars,
Titan and some asteroids in the Solar System have been visited by landers. One of the
main aims of these landers was the to search for any biologic activity by measuring
the surface conditions on these objects. Some space missions conducted to explore the
Solar System carry messages about our civilization. Of course the chance of finding
an extraterrestrial civilization through these space vehicles is extremely low.
• Passive search: this comprises all methods to detect (i) planets, (ii) speculate about
satellites of these planets, (iii) find spectroscopic signatures of biologic activity
(biomarkers) such as oxygen, ozone, methane and other compounds in a planetary
Examples of radio messages sent to different objects are given. No answer has been received
The main message of this chapter is that from several arguments we can conclude that our
civilization might not be the only one in the Galaxy and that we should belong to the older
generation of civilizations at least in the Galaxy.
Extraterrestrial life; biomarkers; Drake Equation; Moon; Mars; Venus; Europa;
Titan; Mars: rovers; SETI; interstellar communication; radio messages
Institute of Physics, Univ. Graz, Austria