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The Search for Aliens - Is There Anyone Else Out There?

Designs of Alien Life

Mars Quiz

Mars today
Mars today

Facts: Before space exploration, Mars was considered the best candidate for harboring extraterrestrial life. But now we know that the surface of Mars is frigid, dry and windswept and with an atmosphere inhospitable to life as we know it. If scientists are to discover life on Mars, it could be in a form that they have not yet considered, for example in ice at the poles or in minute traces of water that may still exist somewhere on the planet.

Artist's Conception: Many scientists believe that the channels and gouges on the Martian surface may have been caused by water that once existed on the planet. Hagen set out to imagine what might have existed on Mars 3.8 billion years ago, a time when scientists believe Mars and Earth had parallel evolutionary development, including the elements needed to sustain life: a dense atmosphere, abundant liquid water, and temperatures above freezing.

Mars then
What Mars may have looked like 3.8 billion years ago.

Although current knowledge suggests that Mars' warm, wet period was too brief to evolve complex life, it is an interesting exercise to speculate on what might have evolved in sustained habitable niches. Hagen has imagined that Mars' plant and animal ecology developed in the oceans and the wet margins of land, and that the base of the chain of life on Mars was photosynthesis.

According to Hagen's vision, varieties of zooplankton thrived and provided food for larger and more complex species. Sponges appeared first with very simple cell types, followed by Martian metazoa that are similar to Earth's jellyfish and anemones. In this imaginary scenario, creatures evolved and swam the deep subsurface rivers and lakes where liquid water was sustained by geothermal warmth long after it disappeared from the surface.

Can you guess?