Earth's oldest fossils yet discovered, give hope for life on Mars

Life on Earth may have begun even earlier than biologists suspected, at a time when the solar system was still in its infancy. Newly discovered fossils in Quebec suggest microbes were hanging out in hydrothermal vents at least 3.8 billion years ago. And if life could have popped up on Earth so early in its history, it's possible it did on other young planets with water on their surface — which bodes well for the prospect of life on Mars, at least in its ancient past.

Reporting their findings in the journal Nature, an international team led by researchers at University College London explain that the fossils aren't of the ancient bacteria themselves. Rather, what they have discovered encased in quartz are little tubes and filaments made of the iron ore hematite. Bacteria can create hematite as part of their own biological reactions, and the researchers said that this is by far the most straightforward, plausible explanation for these microscopic structures. While it's conceivable the tubes and filaments could have gotten there through temperature or pressure changes, their analysis suggests these structures most closely resemble those formed by modern bacteria around hydrothermal vents today.

It would have been a simple existence for these microbes, spending their lives hanging out around vents on the seafloor. Not that there would have been much else to do on a still primordial Earth. These bacteria, dating somewhere between 4.3 and 3.8 billion years ago, would have lived during this period when Earth was essentially still under siege from space rocks (the planet only formed about 4.6 billion years ago.)

If this is indeed evidence of the earliest known life on Earth, then it suggests the simplest organisms could emerge on a planet almost immediately, in geological terms. The researchers suggest that's one more reason to think that life could be very common throughout the universe, with it popping up quickly on any world where conditions are favorable.

Ancient Mars would fit the bill there, as it too had liquid surface water at this early juncture. While it's hard to say these things for absolute certain, it's thought that an ocean as well as lakes and rivers covered Mars during a period between 4.1 and 3.7 billion years ago, with more limited water sources hanging on for a while after that. If the development of life is as quick and easy as this new finding would suggest, there's no reason to think Mars couldn't have supported similar microbial life in its own ancient history. And if that's not the case, then the researchers say that means Earth must be special or unusual in ways we still don't fully understand. Either way, the possibilities are seriously intriguing.

Images from NASA on the largest batch of Earth-size, habitable zone planets
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Images from NASA on the largest batch of Earth-size, habitable zone planets
This chart shows, on the top row, artist concepts of the seven planets of TRAPPIST-1 with their orbital periods, distances from their star, radii and masses as compared to those of Earth. On the bottom row, the same numbers are displayed for the bodies of our inner solar system: Mercury, Venus, Earth and Mars. The TRAPPIST-1 planets orbit their star extremely closely, with periods ranging from 1.5 to only about 20 days. This is much shorter than the period of Mercury, which orbits our sun in about 88 days.
This poster imagines what a trip to TRAPPIST-1e might be like.
This artist's concept allows us to imagine what it would be like to stand on the surface of the exoplanet TRAPPIST-1f, located in the TRAPPIST-1 system in the constellation Aquarius.
This data plot shows infrared observations by NASAs Spitzer Space Telescope of a system of seven planets orbiting TRAPPIST-1, an ultracool dwarf star. Over 21 days, Spitzer measured the drop in light as each planet passed in front of the star. Spitzer was able to identify a total of seven rocky worlds, including three in the habitable zone where liquid water might be found.
The TRAPPIST-1 system contains a total of seven planets, all around the size of Earth. Three of them -- TRAPPIST-1e, f and g -- dwell in their star’s so-called “habitable zone.” The habitable zone, or Goldilocks zone, is a band around every star (shown here in green) where astronomers have calculated that temperatures are just right -- not too hot, not too cold -- for liquid water to pool on the surface of an Earth-like world. 

This artist's concept appeared on the February 23rd, 2017 cover of the journal Nature announcing that the TRAPPIST-1 star, an ultra-cool dwarf, has seven Earth-size planets orbiting it. Any of these planets could have liquid water on them. Planets that are farther from the star are more likely to have significant amounts of ice, especially on the side that faces away from the star.


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