If one day we get a visitor from this planet, they'll jump on our planet the same way human astronauts jumped on the Moon.
For example, the Earth is 10 times more massive than Mars, but only has 2.6 times surface g.
Higher gravity means this upper limit will be smaller. All sorts of similar scaling things will change optimum points for structural and energy reasons.
Higher gravity certainly means higher pressure gradient, more pressure per vertical meter of ocean. And high pressure affects protein structure.
It's life, but not as we know it.
Assuming life develops in an ocean, like we did, organisms in water are essentially weightless, regardless of the g force.
https://stsci-opo.org/STScI-01HA2G716KS9YGAGVY1WBVFJ8Y.pdf
Is this approach, like, sane? I'm not a Bayesian statistics expert.
[0] https://global.oup.com/academic/product/planetary-systems-a-...
By having a detailed model, and modern probabilistic techniques:
The planet’s terminator is modelled as a plane-parallel atmosphere in hydrostatic equilibrium, with uniform chemical composition. The chemical abundances and pressure-temperature (P-T) profile are free parameters in the model. The retrieval framework follows a free chemistry approach, whereby the individual mixing ratio of each chemical species is a free parameter.... Our canonical model comprises of 22 free parameters overall: 11 corresponding to the individual mixing ra- tios of the above chemical species, 6 for the P-T profile, 4 for the clouds/hazes and 1 for the reference pressure Pref , defined as the pressure at a fixed planetary radius of 2.61 R⊕. The Bayesian inference and parameter estimation is conducted using the MultiNest nested sam- pling algorithm (Feroz et al. 2009) implemented through PyMultiNest.
(Sections 2.4 and 3.1 from https://stsci-opo.org/STScI-01HA2G716KS9YGAGVY1WBVFJ8Y.pdf)
> And even if there is a detection, it looks like many other models could potentially fit the data...
Name three.
In the paper they analyze 3 models, "no offset", "offset" and "offsetx2". It's strange that they get better fit for CO2 and CH3 en the "offsetx2" model, but in that model the DMS disappears. So there it at least one model.
Also, they analyze common molecules like CO2, CH4, H2O, NH3 and biologically interesting molecules like CH3-S-CH3 (DMS), HCN, CH3-Cl. From the discussion in the paper it looks like the CH3- part is important, so I'd like to see a brute force search with everything that is in https://en.wikipedia.org/wiki/Atmosphere_of_Titan and has a methyl group, like CH3-CCH, CH3-CN. My Chemistry and Astronomy is no so good, so I'd like to add CH3-OH, CH3-NH2, CH3-SH, CH3-CHO and a few more from https://en.wikipedia.org/wiki/List_of_interstellar_and_circu... I removed the ones that are big or has too many oxygen (like CH3-COOH).
The bump at 4.3um looks real, and it seams to be an standard absorción of CO2. https://www.quora.com/Does-CO2-absorb-all-infrared-frequenci...
The bump at 1.2, 1.4 and 2.4um looks real. I found this showing a peak for CH4 at 2.325um. http://www.astrochem.org/data/CH4H2O.php
[Sorry for the sources, but I'm not an expert is spectroscopy.]
My guess is that they assumed something like
a% * CH4 + b% * CO2 + c% * H2O + others
and get the best fit for a%, b%, c%, ... using the white points. Later, using these numbers they draw the blue line.
The peak for DMS is not clear for my untrained eye, so I can't guess what they did there. (Perhaps it's just the best fit.) It would be nice to see the a graph of the blue line they guessed with DMS and a superimposed red line with and atmosphere with an alternative atmosphere where the DMS is replaced with something uninteresting (N2? H2O? More CH4? I have no idea what is uninteresting here.)
[0]: https://stsci-opo.org/STScI-01HA2G716KS9YGAGVY1WBVFJ8Y.pdf
I wonder how old this world is, and how stable its enviroment is/has been. Complex animal life took 3.5 bn years to emerge on Earth, of course that's a meaningless data point by itself but intuitively for this place to have an ecosystem or complex life it needs to be old.
Still, even without this what a wonderful and weird environment.
That being said, there was an experiment (https://www.pnas.org/doi/full/10.1073/pnas.1115323109) which was able to select single cellular organisms to "become multicellular" in a rapid amount of time (<50 generations? been a while since I read it). Which says to me that, theoretically, the process is not hard, it just requires trillions of attemps to evoke something that works.
How certain are we it took that long (the first time)?
I'm not so sure about that. I mean, at the moment both are impossible, but it's much easier to imagine traveling 4ly than 124ly. 4ly can be reached in a single lifetime if you accelerate a shop to .9c, which is technically possible. 124ly is going to be a multigenerational undertaking no matter what. The 248y communication lag is also a much bigger obstacle than an 8y lag.
I think once you can travel 124ly, you can travel 1000+ ly. You need to be completely self-sufficient and you're going to lose contact with home anyway. If you send a robot, you're not going to hear from that robot again in centuries, if ever.
We all sit around knowing to listen to the skies sometime in October of 2185 to hear if the rover found life within the first month of its landing.
If we ever send a team to live there, we'd hear broadcasts of their lives from 125 years prior. A real portal in time - so cool.
Had not heard of dimethyl sulfide before. That's a good keyword to know.
An amazingly long time ago.
It's not a lot of information, not nearly enough to identify surface features on an exoplanet, but it's very useful data if you're trying to identify likely chemical composition of bodies or how hot clouds of gas are.
Given a sufficient quantity of reactants/reagents, could DMS be produced via a natural process, or is this a sufficiently unfavorable reaction that it's unlikely?
2 CH3OH + H2S → (CH3)2S + 2 H2O
I have always read that its impossible, at least within our current knowledge.
the only semi-plausible theory I've ever heard is that Blackholes might one day yield some way of traveling quickly across the universe but nobody has shown anything substantiated around that or anything else.
If you get in a ship and travel to Alpha Centauri at the speed of light, the travel seems instantaneous to you. But the people you leave behind think you've been gone 8 years when you return.
So instead, I propose that when the ship launches, we also propel the rest of the universe in the opposite direction also at the speed of light. Then, when the astronaut is scheduled to return, we propel the entire universe at the speed of light back to its original location.
All of reality undergoes time dilation. And the trip is basically instantaneous for all involved†.
† Note: This form of FTL is mildly costly in regards to energy expenditure.
K2-18b (name of the exo-planet) orbiting star K2-18 was discovered in 2015 but the water was not detected until 2019.
Very unpleasant planet.
What sort of observation or measurement would allow us to identify life on an exoplanet?
There are some more subtle cases, like the one discussed in this paper.
https://arxiv.org/abs/1802.08421
...and an excellent video on the topic:
> DMS is generated by the degradation of dimethylsulfoniopropionate, which is present in many species of marine algae and plants, including dinoflagellates and coccolithophores
Preprint: https://arxiv.org/abs/1909.05218
Figure 2 pp. 14 of the preprint shows much more plausible error bounds on the curve fit. That press release "best fit" curve is merely an artist's conception.
The preprint of the Webb based paper is here [0] from here [1].
[0]: https://stsci-opo.org/STScI-01HA2G716KS9YGAGVY1WBVFJ8Y.pdf
[1]: https://webbtelescope.org/contents/news-releases/2023/news-2...
