June 10, 2013
Note: I want to thank Josh Rodriguez and the other authors who have made contributions to this blog page over the last year. I have been out on medical leave (that continues) but I will resume blogging as my doctor permits.
Your replies and questions based on my blogs often spark new blogs, so keep on participating in the dialogue. Even when a comment comes in that doesn’t generate a blog-size reply, I usually respond to it in the comments group linked following the blog that inspired it. I have prepared many replies to your comments that have yet to be posted, but they will be eventually.
Thank you for sharing the exploration of exoplanets with me.
- Astronomer Steve
Life on Pluto?
A friend of a friend’s daughter, Ashley (age 12), had been thinking about life on Pluto and asked about her ideas. It sparked this blog…
Pluto’s extreme conditions make life as we know it unlikely there. But those conditions don’t rule out life there or anywhere else in the Solar System or among the exoplanet population that continues to grow.
Everywhere we look
The evolution of life on Earth demonstrates that organisms adapt to habitats and expand into others and even make their habitats. We don’t know how life started here, though a start on ocean shores or near hydrothermal vents on the sea floor are possibilities that are popular with many scientists.* Wherever it started, it expanded by creating new species that could live in other environments. Life on Earth has been found free floating high in Earth’s atmosphere, deep in the oceans, swimming in fresh water, crawling in rain forests, living in solid rock underground and in ice at the poles … really, everywhere we look. We also know that it ranges from individual live cells to cooperating groups of similar cells to cooperating groups of specialized cells to organisms with specialized cells all working together to stay alive – plants and animals with organs. Even organisms sometimes group together in colonies, like swarms of bees and termites and humans in cities.
"So it’s very unlikely that we would find Earth-like life on Pluto. Does that exclude “other-life” based on other chemical reactions? No, it doesn’t. But we might have a hard time recognizing it at first."
Life in the lab
While we know some of the chemistry that makes life, we don’t know what the spark is that separates life from chemical reactions in a test tube. We understand many of the chemical reactions involved in life, though, and we know what conditions might speed them up or slow them down (like temperature). Of course, there could be kinds of life, probably not on Earth, that might use other chemical processes that we are not familiar with and might not recognize, at first, as life.
So how does all this apply to Pluto? Well, Pluto is very cold. Its atmosphere freezes and falls like snow to the ground during its autumn and it stays there during most of Pluto’s “year” (the time it takes Pluto to go around the Sun once). The chemical reactions we recognize occurring in organisms come to a halt even in Pluto’s summer temperatures. The water that is so important to life on Earth is solid ice on Pluto. So it’s very unlikely that we would find Earth-like life on Pluto. Does that exclude “other-life” based on other chemical reactions? No, it doesn’t. But we might have a hard time recognizing it at first.
At present I can’t tell Ashley, and no one else can either, if her hypothesis that there are colonies of life on Pluto is right or wrong. We can never prove a negative, but a single positive example can disprove a negative hypothesis.
The beauty of science is that we can create a hypothesis and share it and that stimulates thinking that can lead to wonderful discoveries. We try and collect data to determine if the hypothesis is likely right or wrong. When we have more information, we can at least narrow the possibility of its correctness. Sometimes even good guesses about a hypothesis turn out to be wrong.
Ashley’s curiosity and creative thinking demonstrate that she is a scientist. When we are born we immediately become scientists, exploring the new (to us) environment around us. There’s no reason people of all ages can’t continue exploring and learning about the world – nearby and distant – around them. You just have to observe and wonder.
*One of the mysteries in my life is why many people seem to prefer the suggestion that life started elsewhere, on Mars for instance, and not on Earth. Moving the origin of life to another planet or somewhere “out there” doesn’t make the origin of life any less mysterious. It just moves it farther away from Earth, where we have even less (or no) firsthand knowledge of conditions.