Koichi’s photographs honestly and sympathetically portray aliens who were victims of drought and the Great Depression on Mars.
You know how 宇宙 is space? Well, a person from space is an alien.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well. It will also help to know how to read the word 宇宙 on its own, too.