It doesn't look like they are particularly helpful, but it also doesn't seem like they automatically remove the possibility of life, either. This is especially true when considering that any Martian life would potentially be significantly different than life here.
The oxygen in Earth's atmosphere is not especially conducive to life. It took a lot of evolution to develop tolerance to it. Perchlorate should be similar.
Reminds me of one of my favorite passages from Jurassic Park:
"Think about oxygen. Necessary for life now, but oxygen is actually a metabolic poison, a corrosive glass, like fluorine. When oxygen was first produced as a waste product by certain plant cells some three billion years ago, it created a crisis for all other life on earth. Those plants were polluting the environment, exhaling a lethal gas. Earth eventually had an atmosphere incompatible with life. Nevertheless, life on earth took care of itself."
That book is so incredibly good. When my kids are the right age I am going to give them that book to read so they will get hooked on science. It should be required reading in high school biology classes. Think about a class centered around that book where students do little experiments related to passages like this one. That would be amazing.
When I was in the 8th grade and I wrote my first program in BASIC I came home from school and told my mother "I want to be a programmer- like the guy in Jurassic Park, but not fat."
Indeed. It's not widely known, but oxygen is still rather poisonous to humans. If you breath pure oxygen for over about half a day, your lungs start taking damage.
There's a reason that oxygen and perchlorate are used as rocket oxidizers.
