Astrobiologists are concerned with finding

planets around other stars
moons around other planets
evidence of life coming to earth
life beyond the solar system

c. evidence of life coming to earth .

Explanation:

astrobiologists are mainling concerned with this because the life may carry an unknown pathogen or disease that we are not immune to so it might kill us of or do damage like the black plague . Every other choice does not seem right im pretty sure they would be thrilled for the other options especially life beyond the solar system .  

The correct option is evidence of life coming to earth

Explanation:

Astrobiology is an intra-disciplinary field in science that deals with the study of life outside of the earth-world and seeks to determine how this life can be detected. From this definition, it can be deduced that astrobiologists are concerned with finding evidence of life coming to earth.

NOTE: The last option looks tricky but some of what astrobiologists are concerned about are life within the solar system but outside of earth, hence the last option is not the answer.

there are no atoms