|Public Domain image|
One of the first things we need to determine is the temperature and climate necessary for life. It is in what some consider to be the Habitable Zone. But since Mars is half again further from the sun than Earth, it's a lot colder, and one of the trickier parts of this problem is creating a convincing climate model at any time in its history that produces conditions above freezing. The temperatures on Mars are estimated by infrared thermal mapper data at between 81 °F and −225 °F. And while life can exist in conditions below freezing, it does prove problematic, especially if there was no warmer time for them to evolve and adapt to less than optimal conditions. Being able to support life and being favorable for life are two vastly different things.
We have seen signs which point to the presence of water there in the past. We've seen clouds in Mars' atmosphere, and seen snow falling. Finding water-formed minerals including calcium carbonite, hematite, jarosite, and goethite on its surface also points to larger quantities of water at some time in its history. As water is a basic component of life as we know it, these are big steps toward confirming the presence of life there.
Just the hint of water is hardly an ideal situation for life. About 70% of Earth is covered with water. About 226,000 forms of life on Earth live in our lakes, rivers, streams, and oceans. Life is dependent on water, and far more than just having trace amounts of it around. So how would Mars have gotten that amount of water?
|Size of Tharsis Volcanoes, by the Lunar and Planetary Institute|
Some scientists theorize that the Tharsis Montes, a volcanic bulge containing the largest volcanoes in the solar system, is large enough to have caused changes to the climate of the entire planet. Since these volcanoes are so huge - the tallest has a whopping summit elevation of 59,000 feet - they could have spewed enough water vapor and carbon dioxide to create a much thicker and warmer atmosphere in a series of eruptions. Some estimate the amount of gasses released into the atmosphere could have given Mars a thicker atmosphere than Earth's. And because of the size of this bulge, it's theorized it has affected the spin axis and changed geographic locations of the planet's poles. Based on the picture above, it's not hard to understand why.
The Mars of today and the Mars of eons ago could look drastically different. What is now frozen desert wastelands could have once been fertile plains and forests, and the cradle of life such as we have never seen on Earth. Would life on Mars have been that dissimilar to Earth's? We can probably assume the evolution of carbon-based life forms, but from there all bets are off.
Throughout Earth's history, the predominant phylum has changed several times. Fossil records indicate mammals weren't always the top dog. At one point plants, fish, amphibians, and dinosaurs were all top forms of life here. At one point, so were arthropods.
What if a similar phylum to Earth's arthropoda became dominant? We know from experience they can be very successful, and it's not hard to imagine a Martian landscape covered in giant bugs. Spiders, ants, scorpions, and the like are quite successful in arid lands and severe climates, and cockroaches live goddamn anywhere they want. It wouldn't be the first time someone envisioned bugs living on Mars.
|Camel Spider © by Scott|
Life on Mars could also be on a much different scale than Earth's. While larger life is more impressive and makes for better stories, my bet would be on smaller life. It's easier to imagine them surviving on less water and in more hazardous climates. Larger animals require so much more to be right in their environments, from food sources to temperatures to available space, that it's hard to see them surviving on a planet more hostile and extreme than our own. But given enough time, and assuming you believe in the theories of evolution, it's not hard to visualize a society of intelligent arthropods, at a fraction of our own size, living comfortably in the lands of ancient Mars.
One would, however, assume a completely different evolutionary chain to have happened in the event of life on Mars. Even a small change in environment can produce drastically different results. It's not hard to see where life on Mars would have taken a very different turn from that on Earth.
Mars and Earth are more alike than we might think. While many find it easy to picture something quite alien and different from life here, the reality is that Mars is not that dissimilar to Earth. The image below compares an outcrop of rocks on Earth with a similar outcrop on Mars. Can you tell which is which? You can visit NASA's Mars Exploration Program website to find out. You got it wrong, didn't you?
|Rock Outcrops on Mars and Earth, by NASA|
Certain functions and structures are the easiest and simplest ways of doing things, and that's critical to evolution. Many different types of animals all have the same basic components, primarily because that's the best way to do things. Plants all function in basically the same way. And they most likely will on Mars too, because the basic foundation for life - the chemicals and elements that make up the structure of Mars - is the same as that of Earth.
So it would be no surprise to find life there. It may be a matter of time and effort. Chances are, if we do discover life, it won't be little green men, but rather little green microbes. It won't be nearly as exciting from a layman's point of view, but for science it will be a discovery of monumental proportions. One thing is for sure: Ray Bradbury would have been excited beyond belief to know there really was once life on Mars.