An artist’s concept of Mars four billion years ago. Image: Michael Lentz/NASA Goddard Conceptual Image Lab.
Four billion years ago Mars had a denser atmosphere, a warm wet climate, cloudy blue skies, and quite a lot of water.
NASA’s Goodard Space Flight Center had released an artists’s impression today of what the ancient Martian landscape looked like, with a time lapse to the more familiar barren red vistas of today available on YouTube.
Liquid water cannot exist on Mars today because of the planet’s low surface temperature and atmospheric pressure. However it is present as ice and vapour and evidence of liquid water on Mars include signs of water erosion, flowing channels, and sedimentary layering.
What is not known is whether Mars’ habitable atmosphere lasted long enough for life to emerge. “The only direct evidence for life early in the history of a planet’s evolution is that on Earth,” said Joseph Grebowsky of NASA’s Goddard Space Flight Center. “The earliest evidence for terrestrial life is the organic chemical structure of a rock found on the surface in Greenland. The surface was thought to be from an ancient sea floor sediment. The age of the rock was estimated to be 3.8 billion years, 700 million years from the Earth’s creation. No fossil evidence of life has yet been found from this period.
“The oldest claimed micro-fossils, found in Western Australia, date to 3.5 billion years ago,” he added. “The existence of a potential life-nurturing climate on Mars ended near these times. A comparison between the two planet’s life histories must be done with caution, due to the different chemical compositions of the surfaces, eg, Mars’ chemistry may have been more suitable early on than Earth’s, and different volcanic and meteoroid impact histories. Also, the histories of life on either planet may not have been continuous. Catastrophic events could have killed off all life at one time only to have it start anew.”
Artist’s concept of Mars today. Credit: Michael Lentz/NASA Goddard Conceptual Image Lab.
NASA’s MAVEN mission aims to determine how Mars lost its atmosphere. There are several theories, the most prominent being that the planet lost its atmospheric molecules and its magnetic field, which protected the atmosphere from erosion, due to the impact of solar wind in a process known as sputtering.