- 3154 - PLANETS - which one to move to? Venus is too toxic, hot, and inhospitable. Mars is deadly too. Just as Venus is extremely hot, Mars is frigid cold. Venus has a thick, poisonous atmosphere, but Mars has a paper-thin one. Mars has all that radiation exposure to deal with. How do we choose?
- ----------------------- 3154 - PLANETS - which one to move to?
- There are several other planets. Why stick with this one?
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- It is inevitable that climate change would reach the tipping point. Famine and disease would ravage humanity. A noxious information ecosystem would send society into a conspiracy-fuelled death cycle. To survive, we need to relocate to another planet.
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- The truly inhospitable region of Venus lies far below, near, and at the surface. About 30 miles above the surface, temperatures are actually Earth-like. At this altitude, atmospheric pressure is also similar to Earth at sea level.
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- There is also similar radiation protection at that level. The air isn’t breathable though. Venus, with its relatively hospitable upper atmosphere, can play a role in humanity’s future in space.
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- There are three reasons underlying the better case for Mars. While surface water is only found seasonally and in small amounts laden with toxins, recent discoveries could make potable water possible by looking underground .
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- The soil of Mars is laden with iron and nasty salts, but experiments with growing crops in Mars-like soil have found some success.
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- Rather than building expensive structures or risking inflatable habitats, the Martian series of caves on Mars built by long-dormant volcanoes could create a radiation-shielded environment. Just add oxygen. Perfect.
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- Humanity’s transition to Mars is inevitable. It will happen in four phases. Exploration is the first step before we set up a Mars base, which we can springboard into cities.
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- Like Earth, different groups will settle in, and pursue different values and goals. The planet will bring them new opportunities to practice the forms of governance and beliefs they wish they could on Earth. Mars offers a chance for renewal and a clean slate. And it is a only six-month flight away.
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- The resources of Mars could also be a launching pad for further exploration. Methane and water on the planet can be used to create rocket fuel. After Mars, the next easy jump is the asteroid belt.
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- On Earth, we happily murder microbes all day, every day with mouthwash, antibiotics, household cleaners. Our poisons are as varied as they are effective. And yet, we don’t regard these acts of destruction on our own planet as an ethical issue. So why worry about polluting Mars?
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- Despite sub-Antarctic temperatures, space radiation, and other hazards at least there’s terra firma to stand on and a gateway to the rest of the Solar System and points beyond. Just hope nothing goes wrong that we have not thought of.
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- Beyond Mars and Venus the only terrestrial planet left is Mercury. It is too hot on one side and absolutely frigid on the other. It’s also notoriously hard to get to thanks to the gravity of the Sun. Jupiter’s out because we would fry in a bath of radiation. The other gas planets, Saturn and Uranus aren’t hospitable either.
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- So maybe we just build a generation ship and aim for for the stars, Proxima Centauri? The Habitable Exoplanets Catalog began with the number of potentially habitable exoplanets. Back then, it was made up of just Gliese 667 C f, and the contentious and ever-evolving planets in the Gliese 581 system. Gliese, in this case, refers to a star catalog , while the stars are 20 and 23 light-years away from Earth, respectively, they’re not close to each other.
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- Since then, the number of planets in the catalog has expanded up to 60 potentially habitable worlds , or 24 if we’re being ultra realistic. Are they close enough to their star to be warm, but not too hot, or too cold? This would mean water could exist in its liquid state.
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- Are they somewhere in between Mars and an Earth-and-a-half in radius? This would probably place them close to Earth-mass, and thus likely rocky.
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- If we don’t know the radius, are they less than five times the mass of Earth? This would again make for a planet that, at the upper limit, would be a very heavy but still rocky planet, rather than a gaseous mini-Neptune.
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- Of the 4,375 known exoplanets as of April 16, 2021, this means only 24 of them are potentially habitable. But the right size and distance are only two of the things we need for habitability in reality. Beyond these traits, we don’t have much other information to go on.
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- Alpha Centauri A and B are pretty well known. They’re the closest stars the size of the Sun to Earth. But they aren’t quite the closest star. The two stars orbit each other. But about .12 light-years out, or around 7600 times the distance of the Sun to Earth, they have a faint companion.
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- Alpha Centauri A and B have been known since antiquity and known to be two separate stars since 1689. Their companion, Proxima Centauri, is so small and faint that it wasn’t discovered until 1915.
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- While the Alphas Centauri are 4.37 light-years from Earth, that difference in distance puts Proxima Centauri just a fraction closer to Earth.
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- In 2016, astronomers working as part of the Pale Red Dot project used decades of data on Proxima Centauri to draw out the existence of a possible planet, Proxima Centauri b. This planet is likely around the mass of Earth, and orbits in a tight 11-day loop around its star.
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- While such a close orbit sounds like a recipe for disaster, Mercury, after all, orbits the Sun in 88 days, the small size and mass of Proxima Centauri and its lower temperatures mean that the planet could be habitable, under the right conditions.
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- The star Proxima Centauri is only 20 percent larger than Jupiter and is just 12 percent the mass of the Sun. It’s classified as a red dwarf, also called an M-dwarf star. These stars are the least massive and most common types of stars in the universe. Not surprisingly, many of the planets on PHL’s index are M-dwarf stars. Only three are not.
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- But, that doesn’t mean Proxima Centauri b is much like Earth. With that close an orbit, the planet faces the same side of the star at all times, the same way we only see one face of the Moon. This process is called tidal locking, and it is part of why Mercury is so inhospitable.
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- Most of these planets are probably tidally locked because there are around M-dwarf stars, and even if they have an atmosphere, water will be locked as ice on the dark side, and the dayside will be a desert.
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- But in between the two sides is a little sliver of liminal space that’s neither day nor night, a place of perpetual twilight. That’s where liquid water might exist, and life might flourish.
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- There’s also the problem of atmospheres. Red dwarfs are small stars, but early in their history, they thrash around violently with flares which can blow away the primordial atmospheres of planets out into the cosmos. So we have to hope that Proxima Centauri b was able to regrow an atmosphere and that it’s something like Earth, and not, say, Venus or Mars.
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- In 2015, Belgian astronomers working on the Transiting Planets and Planetesimals Small Telescope (TRAPPIST) project announced a new star, dubbed TRAPPIST-1.
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- It’s small, about the size of Jupiter, and less massive even than Proxima Centauri. In fact, at 8.9 percent the mass of the Sun, it’s barely over the threshold of having enough mass to ignite. TRAPPIST-1 wasn’t alone astronomers announced three Earth-sized planets in orbit. And all three are potentially habitable.
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- The PHL index lists TRAPPIST-1d as the likeliest of all of them to have Earth-like conditions. But it’s not a one-one comparison. The planet is thought to be somewhere in between Mars and Earth in size. It’s got an Earth-like amount of radiation from its star and thus similar temperatures.
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- TRAPPIST-1d may be more Venus-like than we might like for habitability.
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- If we go to TRAPPIST-1 and any one planet isn’t quite right, we could just jump to the next one, most of them are less than a million miles apart. If we don’t like TRAPPIST-1d, then TRAPPIST-1e is a mere 650,000-mile journey. Earth is 238,000 miles from the Moon. It took three days for Apollo astronauts to get to the Moon.
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- The term Goldilocks Zone is sometimes used in place of the habitable zone. Not too hot, not too cold, just right. But TRAPPIST-1 plays with that by making for a Goldilocks system where, in a few days, we can make our way in between the planets. Even the farthest out of the planets is only 1,400,000 miles from its home star.
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- It is only 40 light-years away. Even going half the speed of light makes for an 80-year one-way trip.
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- If we stick to stars like the Sun, suddenly, we don’t have a lot of places nearby to go. Two of the remaining planets around non-M-dwarf stars on the PHL index aren’t an easy shot. Kepler-442 b is nearly 1,200 light-years away. Kepler-62f is 980+ light-years away. We can’t get there.
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- Tau Ceti f is a hefty world. We haven’t seen it directly, but it’s at a minimum four times the mass of Earth. Gravity there would be high. It’s also likely 1.8 times the radius of Earth though we haven’t seen it pass in front of its star, so that’s a rough estimate. It has a 642-day orbit, one of the longest period known habitable exoplanets.
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- Tau Ceti is a Sun-like star, about 78 percent the mass of the Sun, and burns at similar temperatures. (Both are classified as G-stars.) At 12 light-years away, we could get there in 24 years going half the speed of light.
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- It’s not high on the list of the 24 most habitable planets on the list. In fact, it’s 22 on a list of 24.
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- And if Mars and Venus are non-starters, there are still places we can go. They’re just not planets. They’re the water worlds of our Solar System, places like Ceres in the asteroid belt, Europa and Ganymede circling Jupiter, and Enceladus spewing oceanic water out into space.
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- Even Titan looks like a cold version of early Earth with lakes of ethane and methane dotting the surface while an entire ocean of water is trapped deep below. Pluto might have a subsurface ocean.
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- Jupiter has some of the most deadly radiation in our solar system. When the Pioneer 10 probe passed it in 1974, NASA hadn’t correctly predicted just how much radiation it would emit. Even passing what they thought was a “safe” point, the probe was damaged by the radiation.
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- And while Europa and Ganymede are watery ocean worlds underneath an icy crust, they’re within those radiation belts. The ice may protect life below but would endanger or flat-out fry humans above.
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- Callisto is outside the most dangerous parts of the radiation belts It’s the size of the planet Mercury (Ganymede is slightly larger, Callisto slightly smaller) Its heavy cratering gives places to land
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- It’s also made of water ice. This water could be used for drinking after some processing, sure, but it could also be refined into hydroxyzine for rocket fuel.
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- The worlds beyond Earth seem pretty inhospitable. Maybe we better work on saving our home first?
- May 13, 2021 PLANETS - which one to move to? 3154
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