Is Mars “dead”, or is it only sleeping?

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If Martians visited our planet and only had time to meet one person on Earth, there is no question that their perception of our home would depend greatly on who that person was. Meeting a nine-year-old boy would be a vastly different experience than meeting a ninety-year-old man. It’s clear that to get a true idea of what we’re like as a species, they’d need to visit more than one person—and the same is true for us as we explore other planets.

It is this drive for understanding which is encouraging scientists to take a deeper look at the Red Planet. 188金宝搏集团 half the size of Earth, Mars is home a planet-wide desert with a thin atmosphere. Most of the planet’s water is locked in ice and there is virtually no protection from the Sun’s ultraviolet radiation. While that may seem inhabitable from our standards, it turns out our own home planet is a microbial universe, home to life that can exist is some of the most challenging conditions.

There are signs that Mars was once warmer and wetter than it is today—a phenomenon that many scientists attribute to a once-thicker atmosphere and ozone layer. So what happened to the air and water? And what picture does that paint for our own future?

Our own planet has already gone through dramatic climate changes, as evidenced by the ice ages we’ve experienced. By understanding how the climate functions in both worlds, we can better understand why some planets seem to be more suitable for sustaining the conditions for life as we know it.

Maybe the answer lies in the most extreme of conditions on each planet, and the answer could be found through a detailed study of our own polar ice caps as compared to Mars. There is evidence that once Mars had a large-scale, internal magnetic field like Earth which eventually disappeared, leaving the planet unprotected from solar wind. That wind can erode away a planet’s atmosphere over billions of years. As can giant planetary atmospheres. Some of Mars’ many craters already reveal a vast number of layers in the Martian crust, offering a profound glimpse into its history. The layers within these craters on Mars could provide important clues to the Martian past.

So what questions are scientists really trying to answer within the craters of the Red Planet? Bill Steigerwald of NASA says:

Is Mars “dead”, or is it only sleeping? There are tantalizing hints that Mars might have brief returns to the warm and wet condition of its youth in geologically recent times. Could this be is the result of occasional volcanic activity that temporarily thickens the atmosphere? Or perhaps due to the release of subsurface waters from aquifers at times when the Martian climate is more hospitable to liquid water? Even if this does not happen naturally, humans might be able to awaken Mars locally, as they venture there to search for clues to the past or present Martian life.

If the Martian were atmosphere slightly thicker, perhaps as a consequence of a comet impacting the surface and releasing its gases and water vapor, Mars may temporarily warm up enough to allow for liquid water to be stable. The slightly thicker atmosphere would act like a blanket, trapping more of the Sun’s heat and allowing frozen Martian water and carbon dioxide to evaporate or sublimate. This will make the atmosphere even denser, which would allow it to become warmer still in a self-reinforcing cycle. Similar cycles probably have occurred due to climate changes caused by the natural variation in the tilt of the Martian axis of rotation.

Imagine a time when Martian climatic conditions allowed for it to rain on a parched Martian plain. Imagine desert cliffs, which have known only an icy, thin wind, echoing with the pitter-patter of rain, forming shallow salty seas… perhaps reawakening long-dormant habitats. Imagine human explorers on Mars uncovering such past records themselves, ultimately seeking fossil evidence of ancient Martian life, just as the great archeologists of Earth came upon the civilizations of the past?

This is exploration at its most thrilling; understanding other worlds that may have been habitable for life, and it is part of the NASA vision of searching for life to the Universe. However, to make this a reality, we need a detailed understanding of how hospitable planetary environments and climates operate. There is only one example to learn from our own Earth.