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The Unknown/Space

Venus May Once Have Been Habitable

Posted by Templar on
Venus May Once Have Been Habitable

planet venus

Planet Venus. In his 1954 novel Lucky Starr and the Oceans of Venus, science fiction writer Isaac Asimov imagined seas filled with life and underwater cities on our neighboring planet. It wasn’t long, however, before we discovered what really lurks beneath Venus’s thick cloud cover. In the 1960s and 1970s, the United States’ and Soviet Union’s spacecraft found a dense, toxic atmosphere on Venus full of carbon dioxide and clouds of sulfuric acid. On the surface, temperatures were hot enough to melt lead, and the crushing pressure was akin to that found in Earth’s deep oceans.

All of this means that Venus is violently hostile to life. Even so, the planet is so similar to our own celestial body in size, makeup, and location that it’s often referred to as Earth’s twin. And in its distant past, it may have been even more Earthlike—scientists now believe that Venus could have once held oceans and a gentler climate.

A world of difference

planet venus

Billions of years ago, Venus and Earth formed relatively close together from similar materials.

Earth went on to become a wet, mild world ripe for hosting life. On Earth, plate tectonics, which cycles carbon in and out of the atmosphere, make that stable climate possible. When volcanoes erupt, they shoot carbon dioxide out from the planet’s interior. This greenhouse gas traps heat, keeping Earth toasty enough to support life.

If carbon dioxide were allowed to build up, you’d get a hothouse like Venus. However, the Earth slowly recaptures carbon dioxide when it dissolves in rainwater, flows into the ocean, and is used to build carbonate rocks like limestone on the seafloor. As pieces of Earth’s outer shell shift and grind together, they carry carbon back into the mantle.

In other words, plate tectonics powers Earth’s thermostat. Our planet’s restless crust also recycles other nutrients, like phosphorus, that organisms need to survive. While present-day Venus lacks plate tectonics, it may have behaved more like Earth in its early history.

In fact, there is evidence of past water on Venus. Pioneer Venus, an American mission launched in 1978, measured a form of hydrogen called deuterium, also known as heavy hydrogen. On Earth, this isotope is much less common than regular hydrogen. But on Venus, deuterium isn’t quite so rare in comparison to ordinary hydrogen, indicating that a great quantity of the lighter version of the element has vanished.

Venus versus the Earth

planet venus

At some point, though, Venus’s fate diverged from that of Earth’s, and the planet wound up as an ‘uninhabitable hellscape’. It’s not clear why this happened. One possibility is that Venus’s seas began to evaporate because the planet receives more solar energy than Earth. In the upper atmosphere, sunlight would have broken the water vapor into oxygen and hydrogen, which then fled into space. Without water to weaken the crust so it could break up, there could be no plate tectonics as we know it. Venus would have become hotter and hotter as water vapor and carbon dioxide built up in its atmosphere.

Earthlings, take heed

planet venus

The scorching, poisonous place Venus has become can actually give us a glimpse into our own planet’s history.

When the Magellan mission orbited Venus in the 1990s, it took radar images of the planet’s surface that revealed mountains ranges. These features resemble mountains and plains of cooled lava created here on Earth when pieces of crust were jostled about by the sluggish churning of the mantle beneath them, scientists reported in December at the American Geophysical Union meeting in New Orleans. Similar forces might be active on Venus; it’s possible that the planet’s intense heat warms its crust enough that small pieces can slightly detach from the mantle about six to nine miles down. Some of the plains surrounding Venus’s mountains had been deformed, suggesting that blocks of crust could have been moving about pretty recently.

Venus’s surface

planet venus

Back in the 1970s, Venus proved key to our discovery that chlorofluorocarbons—chemicals used in hairspray, air conditioners, and other products—were a threat to the ozone layer. While creating computer models for the atmosphere of Venus, researchers at Harvard and MIT found that chlorine is really good at breaking apart oxygen compounds like ozone. Before long, another group at the University of California, Irvine, had realized that the extra chlorine we were pumping into our atmosphere might be doing the same thing on Earth.

Venus also offers a preview of our future. Over time, stars increase in luminosity. This means that the planets in their orbit will be bathed in more solar energy. For a planet with liquid water and an Earth-like atmosphere, that means a one-way ticket to Venusville.

Jekyll or Hyde?

planet venus

We’re getting better and better at discovering planets beyond our own solar system—including ones about the size of Earth. We can’t study the soil or atmospheres on these planets to find out if they might be amenable to life, though.

Instead, we realize that two worlds that look the same from a distance can in fact be the Jekyll and Hyde of rocky planets.

It’s possible that Venus’s proximity to the sun is the main reason why it turned out so differently from Earth. But there could be other, more subtle forces at work too, like Venus’s lack of a strong magnetic field.

Planning a visit

planet venus

Even though Venus is our closest neighbor, there’s a lot we don’t know about it. The planet’s thick blanket of clouds makes it difficult to observe, although missions like Magellan and Venus Express have taken radar and infrared images of the surface. Those pictures revealed another challenge: The surface of Venus isn’t very heavily cratered, indicating that it hasn’t existed for long enough to get dinged up much.

Then there’s the fact that Venus’s extreme conditions destroy any lander that visits within a matter of hours. This means that funding is harder to secure for Venus than for the Red Planet.

Another mission headed by Glaze – called Venus In situ Composition Investigations (VICI) – was awarded funding to hone its technology for future competitions. It would have sent two landers to visit highland plateaus that are older than the rest of Venus’s surface. These features might be similar to Earth’s continents, which are built from different kinds rock than its oceanic crust. VICI would have fired a laser into these rocks to vaporize a tiny bit of material, then measured the minerals present in both the plasma it had created and in un-vaporized rock. If Venus’s plateaus have a different composition than the rest of the surface, it could mean that water was involved in forming them.

Venus is hard to explore, sure, but it’s not like it hasn’t been done before 40 years ago. To know what to expect on the exoplanets are discovering far away, however, we’ll need to take another trip next door. It’s incredibly important that we get back to Venus.



The Unknown/Aliens

If The Universe Is Teeming With Aliens Then Where Is Everybody?

Posted by Templar on
If The Universe Is Teeming With Aliens Then Where Is Everybody?

Is there alien life?

universe alien life

Is there alien life?

If the Universe is teeming with aliens then where is everybody? It’s one of the biggest conundrums in the Universe, known as the Fermi Paradox. That means that if the Universe is so conducive to life, and if there are so many opportunities for it within our galaxy alone, why isn’t there any evidence (outside of the History Channel of extraterrestrial life?

Life and intelligence

universe molecule

Self-replicating complex molecule

After all, given the fact that the universe is nearly 14 billion years old, while our galaxy itself is only a hundred-thousand light years from end-to-end, shouldn’t all of the potentially habitable planets have been visited, and colonized, by now? There are good news and bad news.

The good news is we’re here! That means we have at least example in the Universe where things worked out in favor of intelligent life. As far as we can tell, this means the following things have happened:

  • A star was born with a planet that orbits it at the right distance for it to be potentially habitable.
  • That planet had the right mix of elements on it, particularly carbon, nitrogen, oxygen, hydrogen and phosphorus, in order to create life-as-we-know-it.
  • Life actually begun, at some point. This means, at the very least, a self-replicating complex molecule found a way to replicate itself. (The “information-encoded” clause distinguishes DNA/RNA-based life from, say, a non-living crystal.)
  • Life succeeded for a long enough time that it evolved not only beyond this simple, primitive state, but into complex, multi-cellular, highly differentiated organisms.
  • At least one of these organisms developed what we consider “intelligence” to be, and used it to learn about their environment.
  • Eventually, before going extinct, these organisms managed to leave their own world, and set out to explore, and possibly colonize and/or inhabit some of the other ones in our galaxy.

Now, there’s no doubt that all but the above-mentioned last step has already happened here on Earth. And there are huge contingents of our society striving to achieve that last one.

But the big question is this:

alien civilizations

Should there really be tens-of-thousands of civilizations just like us?

How common should this occurrence actually be? Should there really be tens-of-thousands of civilizations just like us, or even more advanced, out there right now, in our galaxy alone? Or are we the only ones like us, in the entire history of the observable Universe, who’ve ever existed? Of course, we don’t know. But the fact of the matter is this: we have no right to expect that just because it happened once, here, that any of these steps are at all common! Thankfully, we do have some evidence to tell us that some of the things that happened are, in fact, common.

The stars, for example.

universe star planets

Twenty percent of the stars in our galaxy have planets within their habitable zones

We know there are somewhere between about 200 billion and 400 billion stars in our galaxy. The vast majority of them, about 95 percent, live as long or longer than our Sun. This means that they do have, at least potentially, plenty of time for evolution to take place. And we’ve also learned, through our exoplanet hunts, that perhaps as many as 20 percent of the stars in our galaxy have planets within their habitable zones. In other words, we’re quite confident that, within our galaxy alone, there are literally billions of stars with rocky planets orbiting at the right distance for life to exist, and they’re loaded up with the right kinds and amounts of elements to possibly give rise to life.

The development part is another great unknown.


How likely or rare is the evolution of a human-level of intelligence?

For nearly 3 billion years, life on Earth was no more complex than single-celled, asexually reproducing organisms. Yes, this includes some extraordinary one-celled creatures, like corals and sponges, but still single-celled organisms, nonetheless. But at some point, evolution permitted complex, highly differentiated, multicellular animals to arise. Is that a commonplace occurrence in the Universe? Or is that an extraordinary rarity? Again, we have no quantitative information except this one instance here on Earth. Until we do, we’re really just playing a guess-timation game.

Finally, here we are! The most intelligent species, as far as we know, ever to exist! Even given the existence of life and the evolution of highly complex, highly differentiated creatures, how likely or rare is the evolution of a human-level of intelligence? Our brain-to-body-size ratio dwarfs that of our nearest competitor, the dolphin, by nearly a factor of two, and the next-nearest great ape by a factor of about three. A chimpanzee society might not have the intelligence to understand or explore the Universe, but we certainly are capable! How rare is this level of intelligence? As far as we know, we’re the only species to attain it in the history of Earth, and we have no idea how common this is in the Universe. It could be extremely common, or we could be the only ones.

And finally, what about spacefaring civilizations?

universe colonization

What about the colonization of other worlds?

What about the colonization of other worlds? The fact that we haven’t either contacted or been contacted by another species very likely tells us that all of these things haven’t happened abundantly in our galaxy, but how rare or common is it? The evidence, at this point, points to, at best, not that common. (And, at worst, we might be the first-and-only, and even that’s only if we can get our act together!) But the fact of the matter is, I’ve never thought of the Fermi paradox as very much of a paradox. It’s not at all hard to imagine that the answer to, “Where is everybody?” is that there isn’t anybody else.

If the answer turns out to be that there isn’t anyone else, it’s up to humanity to change that. And if there is somebody else… well, I want to know! Don’t you?


© 2018 siqik

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