Lush Venus? Searing Earth? It could have happened

Lush Venus? Searing Earth? It could have happened
Planets (composite). Credit: Composite image by Arie Wilson Passwaters/Rice University

If conditions had been just a little different an eon ago, there might be plentiful life on Venus and none on Earth.

The idea isn't so far-fetched, according to a hypothesis by Rice University scientists and their colleagues who published their thoughts on -sustaining , the planets' histories and the possibility of finding more in Astrobiology this month.

The researchers maintain that minor evolutionary changes could have altered the fates of both Earth and Venus in ways that scientists may soon be able to model through observation of other solar systems, particularly ones in the process of forming, according to Rice Earth scientist Adrian Lenardic.

The paper, he said, includes "a little bit about the philosophy of science as well as the science itself, and about how we might search in the future. It's a bit of a different spin because we haven't actually done the work, in terms of searching for signs of life outside our solar system, yet. It's about how we go about doing the work."

Lenardic and his colleagues suggested that may lie outside the "Goldilocks zone" in extra-solar systems, and that planets farther from or closer to their suns than Earth may harbor the conditions necessary for life.

The Goldilocks zone has long been defined as the band of space around a star that is not too warm, not too cold, rocky and with the right conditions for maintaining surface water and a breathable atmosphere. But that description, which to date scientists have only been able to calibrate using observations from our own solar system, may be too limiting, Lenardic said.

"For a long time we've been living, effectively, in one experiment, our solar system," he said, channeling his mentor, the late William Kaula. Kaula is considered the father of space geodetics, a system by which all the properties in a planetary system can be quantified. "Although the paper is about planets, in one way it's about old issues that scientists have: the balance between chance and necessity, laws and contingencies, strict determinism and probability.

"But in another way, it asks whether, if you could run the experiment again, would it turn out like this solar system or not? For a long time, it was a purely philosophical question. Now that we're observing solar systems and other planets around other stars, we can ask that as a scientific question.

"If we find a planet (in another solar system) sitting where Venus is that actually has signs of life, we'll know that what we see in our is not universal," he said.

In expanding the notion of habitable zones, the researchers determined that life on Earth itself isn't necessarily a given based on the Goldilocks concept. A nudge this way or that in the conditions that existed early in the planet's formation may have made it inhospitable.

Lush Venus? Searing Earth? It could have happened
Matt Weller, left, and Adrian Lenardic are shown. Credit: Jeff Fitlow/Rice University

By extension, a similarly small variation could have changed the fortunes of Venus, Earth's closest neighbor, preventing it from becoming a burning desert with an atmosphere poisonous to terrestrials.

The paper also questions the idea that plate tectonics is a critical reason Earth harbors life. "There's debate about this, but the Earth in its earliest lifetimes, let's say 2-3 billion years ago, would have looked for all intents and purposes like an alien planet," Lenardic said. "We know the atmosphere was completely different, with no oxygen. There's a debate that plate tectonics might not have been operative.

"Yet there's no argument there was life then, even in this different a setting. The Earth itself could have transitioned between planetary states as it evolved. So we have to ask ourselves as we look at other planets, should we rule out an early Earth-like situation even if there's no sign of oxygen and potentially a tectonic mode distinctly different from the one that operates on our planet at present?

"Habitability is an evolutionary variable," he said. "Understanding how life and a planet co-evolve is something we need to think about."

Lenardic is kicking his ideas into action, spending time this summer at conferences with the engineers designing future space telescopes. The right instruments will greatly enhance the ability to find, characterize and build a database of distant solar systems and their planets, and perhaps even find signs of life.

"There are things that are on the horizon that, when I was a student, it was crazy to even think about," he said. "Our paper is in many ways about imagining, within the laws of physics, chemistry and biology, how things could be over a range of planets, not just the ones we currently have access to. Given that we will have access to more observations, it seems to me we should not limit our imagination as it leads to alternate hypothesis."

Explore further

What are the chances of life on another planet?

More information: A. Lenardic et al, The Solar System of Forking Paths: Bifurcations in Planetary Evolution and the Search for Life-Bearing Planets in Our Galaxy, Astrobiology (2016). DOI: 10.1089/ast.2015.1378
Journal information: Astrobiology

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Jul 05, 2016
"Earth in its earliest lifetimes, let's say 2-3 billion years ago, would have looked for all intents and purposes like an alien planet," Lenardic said.

Agreed, but arguably it goes well beyond that. For all intents and purposes, Earth looked like an alien planet far more often than just 2-3 billion years ago. How about the times it mostly froze over, or when giant reptiles were everywhere. How about when the oxygen content was nearly doubled and dragonflies had 0.65m (2 foot) wingspans?

Since we couldn't even have predicted the amazing course of evolution of Earth, we can only begin to imagine what is out there on a trillion different planets that the Milky Way contains.

Jul 06, 2016
The difference between Earth and Venus is in an independent rotation.
The constant growth of the body allows the emergence of life on the body in a given time period (transition from a planet in the star) and not related to the "Goldilocks zone".
The problem is the Biblical observation of the universe.

"The Wrong Ideas About Life Creating Zones" http://www.svemir...tml#Life

Jul 06, 2016
Some have speculated that Earth had a solid surface within 100 My after formation and late planetary bombardment. Taking this, another speculation was that the moon forming event collision was up to a half a billion years after the above formation. Just about all 'evolution' takes place within about 250Myears, leaving another 150My or so. We also have theories of 'panspermia', or seeding of our world from space....with life. We 'could' have had life here about which we may never know. Some of it could have even been 'intelligent', but may also have been life but not as we know it.

Life is likely the common resident of myriads of planets. Out there. Steven Hawking's warnings should be heeded. We should actually 'presume' life in our exploration of other bodies even in our own star system, and take necessary precautions and quarantines and cleaning and decontaminations during any upcoming manned missions.

Jul 06, 2016
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Jul 06, 2016
The cranks on this site are on these stories faster than a pit bull on a preschooler anymore.

Poor retard. That's why we call you -- SLOW.

Jul 06, 2016
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Jul 07, 2016
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Jul 10, 2016
The cranks on this site are on these stories faster than a pit bull on a preschooler anymore.

Poor retard. That's why we call you -- SLOW.

And why his friends call him Pit bull.

Look at pit bull/suicide vest pretending to have a life....and not be the same idiot. Monkey pretending to be 2 monkeys want a banana? There's an even bigger loser than you walking around here with a virtual platter of them, however he appears to only offer them up to the independent thinkers....sorry.

Aaah i love it when the 2 monkey's one being his sock, debates their numbfounded peceptions out on the forum, gotta see him live in action :D

Jul 10, 2016
There is some speculation that life and the build up of mass from the skeletal remains in the form of limestone, or in the case of the Sulfur-iron oxide reducers, Iron oxide skeletons and layers abound from that era, and so it is thought that a weight buildup sunk part of the mass far enough that it broke the crust at that point and with the extra weight 'slid under' the leading edge of the broken crust and into the mantle, starting a chain reaction that has continued to this point, or, maybe one of the massive impacts did a similar trick, but during a much different atmosphere and life-form type. However, this set off a new set of events, continued vulcanism from the edges of the sunken plates bringing that oxygen and CO2 back to the surface, as well as sulfur and other vital minerals, that and bringing up Uranium etc. with it's radiation from deeper in the earth brought extra mutations to the pool of life as well and it is thought that this may have helped evolution along.

Jul 10, 2016
@Steelwolf: Are you referring to plate tectonic theory which couples it to the biosphere?

That is indeed speculation rather than main theory. There are many possible bio-feedback mechanisms like that, but the problem like with the current work is to quantify the effects.

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