ummary of the three (3) current competing theories of the origin of life on Earth: It arrived from an extraterrestrial source; it originated as a heterotroph; it originated as an autotroph.

Scientists to this day do not know how life came about on Earth. Yet, they continue to study many kinds of evidence and continue their research. At present there are three competing theories one how life on Earth came about.
Life arrived here from an extraterrestrial source. Swedish scientist Svante Arrhenius popularized the idea of panspermia in the early nineties; the concept that life arose outside the Earth and that living things were transported to Earth to seed the planet with life. According to this passage, his theory does not explain how life arose originally, even though it had little scientific support at that time. His theory has been revived and modified after gaining new evidence from the examinations of meteorites and space explorations. Organic molecules are found in many meteorites, and this suggests that life may have existed elsewhere in the solar system. An analysis of a meteorite found in Antarctica in 1996 suggested that from its chemical make up, it was a portion of Mars, also the presence of complex organic molecules and small globules resembles those found on earth. Yet scientists no longer agree that their structures are from microorganisms even though many may disagree.
Explorations on Mars’s surface failed to find evidence of life. But in June and July of 2003, two spacecrafts launched by the National Aeronautics and Space Administration were launched on Mars to explore its surface for signs of life. Much information was gathered, most importantly being that it was possible that liquid water existed in large quantities. No evidence of life was found, but due to the find of water, it gives reason that it could have supported life. It is argued