TRAPPIST-1's exoplanets appear to have migrated closer to TRAPPIST-1 over time until they reached their current orbits. This migration appears to have allowed them to retain too much water to support life:
What [the ASU-Vanderbilt team] found through their analyses was that the relatively "dry" inner planets ("b" and "c") were consistent with having less than 15 percent water by mass (for comparison, Earth is 0.02 percent water by mass). The outer planets ("f" and "g") were consistent with having more than 50 percent water by mass. This equates to the water of hundreds of Earth-oceans. The masses of the TRAPPIST-1 planets continue to be refined, so these proportions must be considered estimates for now, but the general trends seem clear.
"What we are seeing for the first time are Earth-sized planets that have a lot of water or ice on them," said Steven Desch, ASU astrophysicist and contributing author.
But the researchers also found that the ice-rich TRAPPIST-1 planets are much closer to their host star than the ice line. The "ice line" in any solar system, including TRAPPIST-1's, is the distance from the star beyond which water exists as ice and can be accreted into a planet; inside the ice line water exists as vapor and will not be accreted. Through their analyses, the team determined that the TRAPPIST-1 planets must have formed much farther from their star, beyond the ice line, and migrated in to their current orbits close to the host star.
[...] "We typically think having liquid water on a planet as a way to start life, since life, as we know it on Earth, is composed mostly of water and requires it to live," Hinkel explained. "However, a planet that is a water world, or one that doesn't have any surface above the water, does not have the important geochemical or elemental cycles that are absolutely necessary for life."
Also at Phys.org.
Inward migration of the TRAPPIST-1 planets as inferred from their water-rich compositions (DOI: 10.1038/s41550-018-0411-6) (DX) (arXiv)
Related: Powerful Solar Flares Found at TRAPPIST-1 Could Dim Chances for Life
TRAPPIST-1 Older than Our Solar System
Hubble Observations Suggest TRAPPIST-1 Exoplanets Could Have Water
Induction Heating Could Cause TRAPPIST-1 Exoplanets to Melt
Another TRAPPIST-1 Habitability Study
Related Stories
Astronomers have observed enough planetary transits to confirm the existence of seven "Earth-sized" exoplanets orbiting TRAPPIST-1, an ultra-cool (~2550 K) red dwarf star about 39.5 light years away. Three of the exoplanets are located inside the "habitable zone" of their parent star. These three orbit from 0.028 to 0.045 AU away from the star:
Astronomers using the TRAPPIST–South telescope at ESO's La Silla Observatory, the Very Large Telescope (VLT) at Paranal and the NASA Spitzer Space Telescope, as well as other telescopes around the world, have now confirmed the existence of at least seven small planets orbiting the cool red dwarf star TRAPPIST-1. All the planets, labelled TRAPPIST-1b, c, d, e, f, g and h in order of increasing distance from their parent star, have sizes similar to Earth.
The exoplanets are presumed to be tidally locked. The six closest to TRAPPIST-1 have been determined to be rocky, while the seventh, TRAPPIST-1h, requires additional observations to determine its characteristics due to its longer orbital period.
Mass estimates for the planets range from 0.41 Earth masses (M⊕) to 1.38 M⊕. Radii range from 0.76 Earth radii (R⊕) to 1.13 R⊕.
Spitzer, Hubble, and other telescopes will continue to make observations of the TRAPPIST-1 planetary system, but the best data will likely come from the James Webb Space Telescope (JWST), which is scheduled to launch in late 2018. JWST will allow the atmospheres and temperatures of many exoplanets to be characterized, which will help to settle whether the "habitable zones" of red dwarf stars are actually hospitable.
Artist illustrations and data for the TRAPPIST-1 system compared to Mercury, Venus, Mars, and Earth.
Here's a website dedicated to the star.
Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1 (DOI: 10.1038/nature21360) (DX)
The red dwarf strikes again with 42 observed solar flares. Back in February, NASA and ESO announced the discovery of three potentially habitable Earth-like exoplanets in the TRAPPIST-1 system. Astronomers analyzing data from the Kepler space telescope have observed energetic solar flares which they believe could make it less likely that the TRAPPIST-1 system could host life.
Frequent flaring in the TRAPPIST-1 system - unsuited for life? (arXiv:1703.10130)
Related: Probability of CME Impact on Exoplanets Orbiting M Dwarfs and Solar-like Stars (DOI: 10.3847/0004-637X/826/2/195) (DX)
TRAPPIST-1 was known to be at least 500 million years old. Now astronomers estimate it to be between 5.4 and 9.8 billion years old:
Scientists now have a good estimate for the age of one of the most intriguing planetary systems discovered to date– TRAPPIST-1, a system of seven Earth-size worlds orbiting an ultra-cool dwarf star about 40 light-years away. Researchers say in a new study that the TRAPPIST-1 star is quite old: between 5.4 and 9.8 billion years. This is up to twice as old as our own solar system, which formed some 4.5 billion years ago.
[...] At the time of its discovery, scientists believed the TRAPPIST-1 system had to be at least 500 million years old, since it takes stars of TRAPPIST-1's low mass (roughly 8 percent that of the Sun) roughly that long to contract to its minimum size, just a bit larger than the planet Jupiter. However, even this lower age limit was uncertain; in theory, the star could be almost as old as the universe itself. Are the orbits of this compact system of planets stable? Might life have enough time to evolve on any of these worlds?
Previously:
Seven Earth-Sized Exoplanets, Including Three Potentially Habitable, Identified Around TRAPPIST-1
TRAPPIST-1h Orbital Details Confirmed
Hubble Space Telescope observations suggest that the exoplanets orbiting TRAPPIST-1 in the habitable zone could have water on their surfaces, while the planets closer to the star have likely lost any surface water they may have had:
An international team of scientists, led by Swiss astronomer Vincent Bourrier of the Observatoire de l'Université de Genève, used the [Hubble] space telescope to study the amount of ultraviolet light hitting the planets and measure the amount of hydrogen these worlds are venting into space. The results suggest the innermost planets, TRAPPIST-1b and TRAPPIST-1c, could have lost as much as 20 Earth-oceans-worth of water in the last eight billion years. The outer planets, however, including e, f, and g, which orbit in the habitable zone, would have lost less water, and could still retain vast stores of liquid water on the surface.
[...] The researchers used Hubble to measure the amount of ambient hydrogen floating around the TRAPPIST-1 planets as well as the intensity of ultraviolet light coming from the host star, an ultracool dwarf star. The amount of ultraviolet radiation coming from TRAPPIST-1 suggests the inner planets could have lost an enormous amount of water over the eons, something that is supported by the abundant hydrogen surrounding the planets—a possible indicator of water vapor. Most importantly, the radiation hitting the outer planets and the amount of hydrogen surrounding them suggests these worlds, similar to Earth in many ways, might still retain atmospheric water vapor and even liquid water on the surface.
[...] Whether or not these planets could actually support life is still an open question. First of all, the observations from Hubble are not conclusive, and further observations from other observatories as well as computer simulations are required to support or dispute the possibility of water on the TRAPPIST-1 planets.
"While our results suggest that the outer planets are the best candidates to search for water with the upcoming James Webb Space Telescope, they also highlight the need for theoretical studies and complementary observations at all wavelengths to determine the nature of the TRAPPIST-1 planets and their potential habitability," says Bourrier.
Also at Hubble News and Space.com.
Temporal Evolution of the High-Energy Irradiation and Water Content of TRAPPIST-1 Exoplanets
Star's magnetic field could turn habitable-zone planets into magma soup
[A] team of European researchers has identified something else that could have an immense effect on habitability: the star's magnetic field. Under the right conditions, planets close to a star will experience a strong but variable magnetic field, which can cause induction heating. In the case of one system with several habitable zone planets, the induction heating could be strong enough to convert them into oceans of magma.
[...] The European team behind the new report focused on M dwarf stars. Because these are small, relatively cool objects, their habitable zones are close to the star and well within the region where the star's magnetic field is quite strong. They also have magnetic fields that are strong to begin with, sometimes in the area of thousands of Gauss. The magnetic field of our Sun is typically 10 to 1,000 times weaker.
Not all M dwarfs rotate quickly enough for this to matter. Proxima Centauri, which hosts the closest known exoplanet, takes more than 80 days to complete a rotation. But there is a nearby M dwarf that completes a rotation in only three days: TRAPPIST-1, which hosts at least seven planets, three of them in the habitable zone. So, the team decided to model how much of an effect induction heating might have on these bodies.
[...] For TRAPPIST-1c, the third planet out from the star, induction heating reaches more than 60 percent of the heat released in the planet by radioactive decay. That's enough to melt the entire surface, turning it into a magma ocean in nearly all the different model conditions sampled. The same conditions are likely on TRAPPIST-1d, the one in the habitable zone, where induction heating can be above half the amount of heat released by radioactive decay.
Red dwarf exolife killer or a way to expand the habitable zone further out?
Magma oceans and enhanced volcanism on TRAPPIST-1 planets due to induction heating (DOI: 10.1038/s41550-017-0284-0) (DX)
Previously: Seven Earth-Sized Exoplanets, Including Three Potentially Habitable, Identified Around TRAPPIST-1
Powerful Solar Flares Found at TRAPPIST-1 Could Dim Chances for Life
TRAPPIST-1h Orbital Details Confirmed
TRAPPIST-1 Older than Our Solar System
Hubble Observations Suggest TRAPPIST-1 Exoplanets Could Have Water
A study has found that the two outermost TRAPPIST-1 exoplanets are the most likely to be able to retain their atmospheres:
The last thing the planets around the red dwarf star TRAPPIST-1 need is abundant sunshine. Active eruptions and flares from the star would wreak havoc on the rocky planets in orbit. But fortunately, the outer planets might be safe from this barrage of high-energy space weather.
According to a new study in the Proceedings of the National Academy of the Sciences [DOI: 10.1073/pnas.1708010115] [DX], the outer planets of the system could cling on to their atmospheres. This finding is despite previous studies showing that TRAPPIST-1 might be so active that it blows away planetary atmospheres.
[...] The new results show that while all seven planets could retain their atmosphere, the more likely scenario is that the outermost two, -1g and -1h, have the best odds (and -1e and -1f have a weaker chance.)
This could be resolved by JWST observations.
(Score: 1, Funny) by looorg on Thursday March 22 2018, @02:08AM
Silly exoplanets, they felt Gods wrath and there was no Noah around to build an ark for them so all life drowned. Praise divinity!
(Score: 4, Insightful) by Runaway1956 on Thursday March 22 2018, @02:16AM (23 children)
If/when we meet intelligent life, I wonder if that intelligent life will even recognize us as intelligent. We can't imagine how intelligent life might evolve on a water world, so we dismiss the possibility. Like, intelligence can't possibly evolve without first mastering fire, right?
Life as we know it is the only possible life.
How about we wait until we can at least send a probe, before we consign a planet to lifelessness.
(Score: 0) by Anonymous Coward on Thursday March 22 2018, @03:09AM (11 children)
Why should land surfaces even be required? We still don't have 100% proof of how and where life started on Earth. It may take a few billion years longer without land surfaces (e.g. just the right sequence of cosmic rays to zap stuff near a hydrothermal vent) but so what?
And that's just for life as we know it.
(Score: 5, Insightful) by takyon on Thursday March 22 2018, @04:10AM (10 children)
There's a little more to the story than "Wow, it's covered with water":
https://www.sciencemag.org/news/2015/08/why-water-worlds-won-t-host-life [sciencemag.org]
And from the arXiv for this paper:
https://arxiv.org/abs/1706.02689 [arxiv.org]
There could also be a pressure problem if these planets have oceans that are hundreds of times more massive than Earth's, along with higher gravity in some cases.
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 2) by captain normal on Thursday March 22 2018, @05:16AM (9 children)
Here on Earth we have many forms of life that live and go down into depths like the Marinas Trench where pressures are huge compared to the surface pressures. High pressure is a bogus argument.
When life isn't going right, go left.
(Score: 3, Insightful) by takyon on Thursday March 22 2018, @05:19AM (6 children)
And if the pressure was 100 times greater than in the Mariana Trench?
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 2) by Bot on Thursday March 22 2018, @06:34AM (3 children)
it does not matter really. life is about behavior not chemical composition, the good old grow multiply populate, it may happen at vastly different time scales/conditions. It is not even a theological problem as somebody liked to reduce it to. Adam and Eve are the pinnacle of creation as physical entities able to recognize their creator or something like it. Not necessarily because they are the first or the only ones.
Account abandoned.
(Score: 2) by Reziac on Friday March 23 2018, @03:11AM (2 children)
By that definition, the Yellowstone Hot Spot is alive.
And there is no Alkibiades to come back and save us from ourselves.
(Score: 3, Touché) by Bot on Saturday March 24 2018, @02:39PM (1 child)
Does it populate, that is morphologically adapt to different conditions and spread? Then it is alive.
Don't be a carbon-based-life-form-ist.
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(Score: 2) by Reziac on Saturday March 24 2018, @03:32PM
LOL! modded up. :D
And there is no Alkibiades to come back and save us from ourselves.
(Score: 0) by Anonymous Coward on Thursday March 22 2018, @08:16AM
You are getting very close to an old creationist argument: Earth is so perfect for life that it must have been created by an intelligent designer to have exactly the properties that life needs. No. This life evolved on Earth, and thus the properties of Earth are the properties that life evolved to live in.
Life on a planet where the oceans have 100 times greater pressure will evolve to live in oceans with 100 times greater pressure.
(Score: 4, Interesting) by Immerman on Thursday March 22 2018, @01:15PM
Waterborn life is, generally speaking, neutrally buoyant - life evolved for a particular depth range generally remains there without trouble. Sure, it may occasionally get caught in a down-current and crushed by the pressure, but so long as that doesn't happen to the entire population, it's not really a problem.
Meanwhile, deep-sea life doesn't suffer any ill effects from the pressure, since its internal pressure matches that of it's environment - in fact being pulled to the surface would be fatal as its cells rupture and/or dissolved gasses come out of solution.
The only reason pressure would be a problem is if it interfered with chemical processes - and given that liquids are relatively incompressible that doesn't really happen - chemical reactivity in a gas increases with pressure (more molecular collisions per second), but it has negligible effect on solids or liquids.
(Score: 4, Informative) by PinkyGigglebrain on Thursday March 22 2018, @04:12PM (1 child)
Not entirly. Deep-sea pressures do affect chemical reaction rates somewhat, speeding up reactions. Organisms adapted to these pressures may experience metabolic problems when brought to the surface for study. [noaa.gov].
BUT, that does not preclude life evolving under the extreme pressures of one of these worlds. As to the whole "..does not have the important geochemical or elemental cycles ..." bit I call BS. Deep sea geothermal vents put plenty of the needed elements for life into the water, I've read several recent theories that say the vents might have been where life started on Earth.
If there is one thing about life that is probably a Universal trait it is that if there is any chance at all it WILL happen.
"Beware those who would deny you Knowledge, For in their hearts they dream themselves your Master."
(Score: 2) by Bot on Saturday March 24 2018, @02:44PM
Indeed life is more stable than the immutable.
Just as freedom with rules is often more free than literal anarchy.
That is, GPL > BSD license.
Done trolling for the day, have a nice weekend.
Account abandoned.
(Score: 4, Insightful) by JoeMerchant on Thursday March 22 2018, @04:05AM
They're thinking that the water-land interface is critical to "life as we know it" and I'm not sure I even agree with that.
Certainly, life would be different without a terrestrial space for evolution to take place in, but with an ocean a few hundred miles deep you could get some very interesting chemical reactions going around hydrothermal vents, and possibly some Earth-like stuff going on near floating rocks too. Once evolution started, who knows what might come out of a volume of water that large and deep.
🌻🌻 [google.com]
(Score: 2) by captain normal on Thursday March 22 2018, @05:09AM
Agree, I've spent enough time on the ocean to know there is abundant life in the water. Also there many ocean mammals that are very intelligent. They may not be building weapons, rocket ships or generally making a big mess of their planet, but dumb they are not.
When life isn't going right, go left.
(Score: 0) by Anonymous Coward on Thursday March 22 2018, @06:16AM (2 children)
Unless they are too primitive to know that space probes which broadcast at them via directional antennae aren't a natural occurrence then they will notice.
>inb4 what if they don't know about electromagnetism
Then they're idiots or underdeveloped.
(Score: 0) by Anonymous Coward on Thursday March 22 2018, @08:24AM (1 child)
I recall an old comic where an ant explains to the other ants "we have looked for every known form of smell-based communication, and the conclusion is clear: There is no intelligent life up there".
Your space probe will not look much different from a magnetic rock to any space faring species (that does not include us, our couple of visits to the local moon doesn't count). Electromagnetic communication is simply too slow to be useful. And we won't be able to detect their faster-than-light communication at all.
(Score: 0) by Anonymous Coward on Friday March 23 2018, @08:19AM
Sure we could be missing something, but there's probably not as many fundamental fields as there are possible molecules which can be practically smelled.
(Score: 1, Interesting) by Anonymous Coward on Thursday March 22 2018, @10:03AM
So there is life and intelligent life, not exactly the same. This is about life.
We know from here on Earth that life can develop various strategies (e.g. chemotropism) to complement geochemical and elemental cycles. Even stronger stated, life is often an important component of elemental cycles on Earth.
Sure, things might be slower to bootstrap life, but life will find ways to complement the things it finds limiting.
(Score: 2) by maxwell demon on Thursday March 22 2018, @12:16PM
There's a story by Stanislav Lem (I think it was in the Star Diaries) where the protagonist visits a school on another planet, where the final exam is going on. One of the questions of that exam is: "Explain why there cannot be any life on Earth."
The Tao of math: The numbers you can count are not the real numbers.
(Score: 0) by Anonymous Coward on Thursday March 22 2018, @12:52PM
Given this, how can scientists expect to find life on Jupiter's moons then? NASA has spent a lot of time discussing that possibility, and this would seem to totally discredit that notion.
(Score: 2) by DannyB on Thursday March 22 2018, @05:00PM (1 child)
Imagine a conversation on some planet, discussing whether the life on some other planet is intelligent.
Since we are a winged species with flight, it is clear, and all experts agree, that the development of flight is a prerequisite to the development of intelligence. Therefore none of the life on the subject planet of study could possibly be intelligent.
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(Score: 2) by DannyB on Thursday March 22 2018, @05:00PM
Use that as an analogy for whether you would recognize life or not.
To transfer files: right-click on file, pick Copy. Unplug mouse, plug mouse into other computer. Right-click, paste.
(Score: 2) by ants_in_pants on Thursday March 22 2018, @09:51PM
more like, we don't know for sure that life can exist in this environment, and previous experiences with e.g. the Moon and Mars indicate that most environments do not support life.
-Love, ants_in_pants
(Score: 3, Funny) by coolgopher on Thursday March 22 2018, @02:16AM (3 children)
It could be life Jim, just not life as we know it.
(Score: 1) by tftp on Thursday March 22 2018, @02:38AM
(Score: 0) by Anonymous Coward on Thursday March 22 2018, @03:10AM (1 child)
You can grab an octopus by the octopussy there when you're a star
(Score: 2) by maxwell demon on Thursday March 22 2018, @12:18PM
You surely meant: "when you're a sea star".
The Tao of math: The numbers you can count are not the real numbers.
(Score: 2) by HiThere on Thursday March 22 2018, @06:09PM
From the summary it looked to me as if he was really arguing that they wouldn't be able to detect life via spectroscopic analysis of the atmosphere. And that seems plausible.
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