I hear parents from previous generations say the above when you mention something like car seats, bike helmets, or not snacking on lead paint chips. And honestly, I understand that reaction now.

If I'm lucky enough to have grandkids, I'm sure I'll hear about how terrible the things I did for my kids were. "OMG, did you seriously feed me broccoli?? How could you not have known what it would do to my IQ — I mean it is so obvious!"

Imagine how NASA feels now that they know they killed life on Mars? How did they know what they were doing was going to, 30 years later, turn out to have been a bad idea?

In the 1970s, the Viking mission found no signs of life.

But it was looking for Earth-like life, in which salt water is the internal liquid of living cells.

Given the cold dry conditions of Mars, life could have evolved on Mars with the key internal fluid consisting of a mix of water and hydrogen peroxide, said Schulze-Makuch.

One Viking experiment seeking life on Mars poured water on soil. That would have essentially drowned hydrogen peroxide-based life, he said. And different experiment heated the soil to see if something would happen which would have baked Martian microbes.

"The problem was that they didn't have any clue about the environment on Mars at that time," Schulze-Makuch said.
Associated Press

So the moral of the story is to just keep on truckin'. Do what feels right in your gut, and fight with your kids about it in 30 years.