How close to Earth is your ELW? A scoring method

[marx]

Anyone who's seen a bunch of Earth-like worlds probably noticed that while they are all Earth-like, some are more like Earth than others. Sure, they are all habitable (or at least should be), but some of them would still be considerably more uncomfortable to live on than others. I was recently thinking about looking for the most Earth-like planets, and to make comparison easier, I came up with a relatively simple scoring system. So, presenting the MESS, Marx's Earth-like Scoring System:

https://docs.google.com/spreadsheets/d/19bXzw7N4_2QKISF0eAnFz6Gz2a_O4GJiw0ttfFBfKW0/edit?usp=sharing

You can edit the "Target" cells and get a numerical score on how close to Earth your ELW is. (Or just make a copy of your own of the spreadsheet.) The lower the score, the closer it is: a perfect match would be 0. Do bear in mind that this is not an absolutely objective guide, it's still somewhat subjective due to how factors are weighted. But it should still be quite useful to more accurately measure how Earth-like your finds are than just looking at their numbers.
Sorry, there's no app or anything to automate this, I just did this as an experiment. If anyone wants to use it anywhere, feel free to do so!


Now, about how the scoring works. It's fairly simple: the relative difference is multiplied by one of two weights, depending on whether the target's characteristic is under or above Earth's. This weighing is because some things are more important to would-be colonists than others. For example, you can manipulate the temperature inside a building, or you could just move to a milder climate - but you can't manipulate the gravity, which is also global.
For a detailed explanation of how I classified the importance of factors, and why, click the spoiler:

Spoiler

Gravity: very important. There's no way of changing this, so all you can do is adapt to it. While the effects of lower versus higher gravity on the human body are rather uncertain, as far as I know. I still went with lower being better than higher, simply due to building construction being easier in lower gravity.

Surface temperature: low importance. Colonists can settle in different climates, move farther / closer from the equator, and so on. This would actually be interesting to note roughly how much land on an ELW is habitable, but since we have no figures on how much of a planet's surface is land and how much is covered by water, it's not like we can do that. (This is also why I chose to leave the radius of the planet out from the comparison.) Also, I decided to give lower temperatures a bit better weight than higher ones.

Surface pressure: low importance. New arrivals will need some time to adjust, but should be fine otherwise. Lower than Earth pressure is a bit worse than higher though.

For the atmospheric components, I didn't go with the percentages, but rather the partial pressure of them. The calculation for those is simple: atmospheric pressure * component percentage.

Nitrogen partial pressure: low importance. As far as I can tell, the game makes certain that nitrogen levels in the atmosphere wouldn't be toxic. But IANAD - I Am Not A Diver.

Oxygen partial pressure: moderate importance, especially if it's lower than Earth's. That might make it more difficult for people to adapt.

Orbital period: low importance. Might get boring for people if years and seasons are long, but they should be able to get used to it easily. Also, let's not forget that the game counts the orbital period of the parent body, which might not be a star!

Rotational period: high importance. Longer days might be difficult for people to adapt to, and lower ones would even more so - and there isn't much they can do to change this. (Besides staying in buildings a lot, of course.) For example, in case there's a binary pair of Earth-likes, the game will say their orbital period is 80 days, but they'll likely orbit their parent star in a much longer period than that. (Or, to be more precise, the barycentre of the two will orbit the star.)

Axis tilt: low importance. Seasons are nice and all, but there are more important things to consider.

Number of moons: high importance if there are none, medium if there are two or more. Tides would be important, and if there's no moon, the tides from the star would be much lower. If there are more moons than one, that might produce interesting tide patterns, depending on their configuration. So this is a simplification.

Number of stars: medium importance. If there is more than one star in the system, then depending on their relative brightnesses, orbits and such, they might result in complex day-night cycles. Unfortunately, you can't see this in-game, as the engine doesn't track more than one light source, but you could check it in EGO's orrery, for example. And while us Commanders might appreciate a seemingly-chaotic dance of light and dark, I'm fairly certain the colonists down on the planet wouldn't.

Of course, the weights could probably use some tweaking, and it might have been better to go with a non-linear calculation, but I wanted to keep it simple. If anyone has suggestion on how to improve it, feel free to share!

So, what's your most Earth-like world?

 

[Traesha]

Here is one 41.67, not sure how much closer I can get atm:

Spoiler

I have quiet a list of ELW's to get through one's I get back to the bubble. This one I allready got when I docked in Colonia system.
Since you mention rotational period to be of high importance, that kinda makes earth-likes orbiting class A & M stars "less perfect" then for example earth-likes around F & K stars and likely G stars the best... since Earth in Sol orbits as we know.. a class G star.

Anyways, I wouldn't mind days that last for 36hrs [wink] but I like the higher temperature and the surface pressure and oxygen lvl to be close to that of earth. Low gravity is a bonus as well IMO.

 

[Sapyx]

I have my own, much simpler system for calculating Earth-like-ness: My "Parallel Earth Index" checks eight parameters (mass, gravity, temperature, pressure, volcanism, atmospheric composition, day length and orbiting objects (rings/moons)). If a parameter matches near enough, the planet gets a point. Theoretical maximum score is eight points; my highest so far is four points.

"Near enough" is somewhat subjective for each parameter. Climatologists say a 2 degree temperature difference would be catastrophic for Earth, so I set the target temperature range to be within 2 degrees of Earth-normal (288 K). Gravity, on the other hand, has a fairly broad range (0.9 to 1.1).

Two things neither of our scales take into account, and probably should, are extreme axial tilt and tidal locking to the star. Both of these have the potential to create an "Earth-like planet" that is definitely non-Earth-like in terms of habitability: a tidally-locked planet is likely only going to be comfortable in the thin ribbon of surface around the terminator, while a planet with an extreme, Uranus-like axial tilt would likely force any inhabitants to take up a nomadic existence, fleeing the extreme seasons, especially if the year was long.

And you also mentioned the desirability of a moon, with respect to tides. The Earth would still have tides if you took the Moon away: the tides caused by the Sun. They'd only be a third of the height of our current tides and they'd be locked to the Sun, happening at the exact same time each day, but there would still be tides. Any non-tidally-locked planet should have tides.

 

[marx]

First off, thanks for the feedback! New ideas are always good to think on.

Two things neither of our scales take into account, and probably should, are extreme axial tilt and tidal locking to the star. Both of these have the potential to create an "Earth-like planet" that is definitely non-Earth-like in terms of habitability: a tidally-locked planet is likely only going to be comfortable in the thin ribbon of surface around the terminator, while a planet with an extreme, Uranus-like axial tilt would likely force any inhabitants to take up a nomadic existence, fleeing the extreme seasons, especially if the year was long.

A good point, one I've forgotten. I've just now thought about adding this to the calculation, with a very large weight added if the planet is tidally locked to a star, but to be fair said tidal lock would pretty much be enough to disqualify a planet.
Perhaps the presence of multiple stars in a system could "save" such a planet, but only if it's not in a circumbinary/trinary/etc orbit around them.

And you also mentioned the desirability of a moon, with respect to tides. The Earth would still have tides if you took the Moon away: the tides caused by the Sun. They'd only be a third of the height of our current tides and they'd be locked to the Sun, happening at the exact same time each day, but there would still be tides. Any non-tidally-locked planet should have tides.

Yes, but like you wrote, said tides would be much lower. (Oops, looks like I made a mistake when I originally wrote the post. I've fixed that.) From what I've read, large tides might have been important in the formation of life, although IANAB. But they'd certainly help the marine ecosystems of the planet. And well, Earth does have a moon, so a planet that doesn't (or has more than one) is less Earth-like.

 

[Friedenreich Xante]

The moon might be overwhelmingly important for our Ecosystem, but its importance bows down to Zero when it Comes to human habitation. If the ecosystem on the new planet is fine without it, why bother. You both overrate it too much.

On the other Hand, I cannot understand how tidally locked ELW can even exist. There are not remotely like earth. Imagine the enormous storms that occur on that planet, while the intensly warm and the freezing cold side of the atmosphere struggle to mix with winds of several hundreds of KM/H. There may be water, there may be earth, but the life on the surface, if it manages to exist, is very different from us. I'd even say, the slower the Rotation, the worse for habitability. Short days are fine.

Extreme axis tilt can also be disqualifying for those ELW. At some Point you get back to the Problems of a tidally locked planets (except at equinoxes), because its rotating axis is directed toward the star, so Rotation has nearly no effect on Illumination, especially at solstice.

 

[newman1702]

That reminds me, I have a ton of ELW's for your list, I never seem to get around to giving them to you. Just too much work to list them all in a way compatible with your records

 

[Cmdr Coddiwompler]

Anyone who's seen a bunch of Earth-like worlds probably noticed that while they are all Earth-like, some are more like Earth than others. Sure, they are all habitable (or at least should be), but some of them would still be considerably more uncomfortable to live on than others. I was recently thinking about looking for the most Earth-like planets, and to make comparison easier, I came up with a relatively simple scoring system. So, presenting the MESS, Marx's Earth-like Scoring System:

https://docs.google.com/spreadsheets/d/19bXzw7N4_2QKISF0eAnFz6Gz2a_O4GJiw0ttfFBfKW0/edit?usp=sharing

You can edit the "Target" cells and get a numerical score on how close to Earth your ELW is. (Or just make a copy of your own of the spreadsheet.) The lower the score, the closer it is: a perfect match would be 0. Do bear in mind that this is not an absolutely objective guide, it's still somewhat subjective due to how factors are weighted. But it should still be quite useful to more accurately measure how Earth-like your finds are than just looking at their numbers.
Sorry, there's no app or anything to automate this, I just did this as an experiment. If anyone wants to use it anywhere, feel free to do so!


Now, about how the scoring works. It's fairly simple: the relative difference is multiplied by one of two weights, depending on whether the target's characteristic is under or above Earth's. This weighing is because some things are more important to would-be colonists than others. For example, you can manipulate the temperature inside a building, or you could just move to a milder climate - but you can't manipulate the gravity, which is also global.
For a detailed explanation of how I classified the importance of factors, and why, click the spoiler:

Spoiler

Gravity: very important. There's no way of changing this, so all you can do is adapt to it. While the effects of lower versus higher gravity on the human body are rather uncertain, as far as I know. I still went with lower being better than higher, simply due to building construction being easier in lower gravity.

Surface temperature: low importance. Colonists can settle in different climates, move farther / closer from the equator, and so on. This would actually be interesting to note roughly how much land on an ELW is habitable, but since we have no figures on how much of a planet's surface is land and how much is covered by water, it's not like we can do that. (This is also why I chose to leave the radius of the planet out from the comparison.) Also, I decided to give lower temperatures a bit better weight than higher ones.

Surface pressure: low importance. New arrivals will need some time to adjust, but should be fine otherwise. Lower than Earth pressure is a bit worse than higher though.

For the atmospheric components, I didn't go with the percentages, but rather the partial pressure of them. The calculation for those is simple: atmospheric pressure * component percentage.

Nitrogen partial pressure: low importance. As far as I can tell, the game makes certain that nitrogen levels in the atmosphere wouldn't be toxic. But IANAD - I Am Not A Diver.

Oxygen partial pressure: moderate importance, especially if it's lower than Earth's. That might make it more difficult for people to adapt.

Orbital period: low importance. Might get boring for people if years and seasons are long, but they should be able to get used to it easily. Also, let's not forget that the game counts the orbital period of the parent body, which might not be a star!

Rotational period: high importance. Longer days might be difficult for people to adapt to, and lower ones would even more so - and there isn't much they can do to change this. (Besides staying in buildings a lot, of course.) For example, in case there's a binary pair of Earth-likes, the game will say their orbital period is 80 days, but they'll likely orbit their parent star in a much longer period than that. (Or, to be more precise, the barycentre of the two will orbit the star.)

Axis tilt: low importance. Seasons are nice and all, but there are more important things to consider.

Number of moons: high importance if there are none, medium if there are two or more. Tides would be important, and if there's no moon, the tides from the star would be much lower. If there are more moons than one, that might produce interesting tide patterns, depending on their configuration. So this is a simplification.

Number of stars: medium importance. If there is more than one star in the system, then depending on their relative brightnesses, orbits and such, they might result in complex day-night cycles. Unfortunately, you can't see this in-game, as the engine doesn't track more than one light source, but you could check it in EGO's orrery, for example. And while us Commanders might appreciate a seemingly-chaotic dance of light and dark, I'm fairly certain the colonists down on the planet wouldn't.

Of course, the weights could probably use some tweaking, and it might have been better to go with a non-linear calculation, but I wanted to keep it simple. If anyone has suggestion on how to improve it, feel free to share!

So, what's your most Earth-like world?

Digging up an old thread as this came up in a discussion in the Observatory Core discord recently and I was thinking of implementing something along this line in one of my plugins (called StatScanner which, among other things, tracks personal bests and checks if you found a potential galactic record OR procgen record). Eahlstan pointed me here.

I like this idea overall and the relative simplicity of the scoring math, did you gather any further tweaks/ideas that you didn't get around to updating putting into the spreadsheet but meant to?

Feel free to reach out via discord (ie. Observatory Core discord) if you prefer.

Cheers!

 

[marx]

Oh hey, this was a pleasant surprise. Thanks! I'd prefer to reply here, since it's far easier for everyone to search the forums than Discord(s).
I had a few ideas and tweaks, sure, but I never got around to implementing them, because I couldn't really decide on weights at first, and then more important stuff came along anyway. These were:
1. Is the planet tidally locked? Probably terrible if it is, but I doubt that an Earth-like with a good score would end up tidally locked anyway.

2. How elliptic is the orbit? Likely not that much of a problem (unless it's highly elliptic), and the vast majority of ELWs are on near-circular orbits anyway, but it might be something to consider too.

3. What about argon in the atmosphere? This one has always been a fascinating topic, especially on those ELWs where there is more argon than nitrogen. There was discussion here, I brought it up elsewhere, with two divers too, and opinions differed. The consensus seemed to lean towards it not probably being a problem, as long as you weren't breathing in while your lungs were still filled with Earth-air. Except if the partial pressure of it is much higher than Earth's nitrogen's... But well, it's a complex topic, to be distilled into a simple weight here. At the very least, the game certainly has no problem with ELWs having argon in the atmosphere, not just nitrogen.

Of course, knowing more today than back in 2017, there could be more rarities to consider too, like the ELW being inside a planetary nebula, being a trojan or a shepherd moon (or just a "regular" one). At first glance though, I don't think those would impact humans on the surface much.

 

[Eahlstan]

1. Is the planet tidally locked? Probably terrible if it is, but I doubt that an Earth-like with a good score would end up tidally locked anyway.

Tidal locking is irrelevant, synchronous rotation might be a problem.

 

[marx]

When I saw the Eahlstan replied part, I knew you'd be saying this Sure, but the game says "Tidally locked", not "Synchronized rotation", so it's easier to say this.

 

[Eahlstan]

When I saw the Eahlstan replied part, I knew you'd be saying this Sure, but the game says "Tidally locked", not "Synchronized rotation", so it's easier to say this.

Yeah, it says tidally locked on tidally locked bodies. That just means that their orbital characteristics won't ever change (if there's no outside force - like a passing star - applied). A tidally locked ELW that's not in synchronous rotation might actually be more stable in the long run than ELWs that aren't tidally locked.

 

[Cmdr Coddiwompler]

I created a basic custom criteria prototype (requires Observatory Core >= 1.x I suspect) that checks all the things in your sheet plus the items above (with somewhat arbitrary weights) -- except moons (which can't be reliably determined in Custom Criteria as currently implemented). When scanning nav beacons (like for Sol) stars are not guaranteed to be known before you encounter the body, and as such multiple stars here may not be properly detected either. Critique/comments welcome.

Earth checks out at least.

A good match from my main commander:

{
  "timestamp": "2023-06-05T03:06:31Z",
  "event": "Scan",
  "ScanType": "Detailed",
  "BodyName": "Spliergh TA-K c23-0 1",
  "BodyID": 1,
  "Parents": [
    {
      "Star": 0
    }
  ],
  "StarSystem": "Spliergh TA-K c23-0",
  "SystemAddress": 97945749706,
  "DistanceFromArrivalLS": 412.520270,
  "TidalLock": false,
  "TerraformState": "",
  "PlanetClass": "Earthlike body",
  "Atmosphere": "",
  "AtmosphereType": "EarthLike",
  "AtmosphereComposition": [
    {
      "Name": "Nitrogen",
      "Percent": 81.502975
    },
    {
      "Name": "Oxygen",
      "Percent": 17.892630
    },
    {
      "Name": "Water",
      "Percent": 0.579138
    }
  ],
  "Volcanism": "",
  "MassEM": 0.428283,
  "Radius": 4706859.000000,
  "SurfaceGravity": 7.705092,
  "SurfaceTemperature": 315.724670,
  "SurfacePressure": 88490.554688,
  "Landable": false,
  "Composition": {
    "Ice": 0.000000,
    "Rock": 0.674102,
    "Metal": 0.325898
  },
  "SemiMajorAxis": 123599588871.002197,
  "Eccentricity": 0.000813,
  "OrbitalInclination": 0.001306,
  "Periapsis": 19.018218,
  "OrbitalPeriod": 26545828.580856,
  "AscendingNode": 74.184877,
  "MeanAnomaly": 225.194909,
  "RotationPeriod": 80044.520763,
  "AxialTilt": -0.365010,
  "WasDiscovered": false,
  "WasMapped": false
}

Using your sheet, I can get the same number:

Edited to add the extra checks, use exact same calculations/conversions from the CC and fixed a bug with calculating Oxygen PP from your sheet.

---@Global
-- For ELW Similarity Score
---@param factor number
---@param posWeight number
---@param negWeight number
---@return number
function WeightedScore(factor, posWeight, negWeight)
  if factor >= 0 then
    return factor * posWeight
  else
    return factor * negWeight * -1
  end
end
---@End

---@Complex ELW Similarity Score
local EarthG = gravityAsG(9.797759)
local EarthTemp = 288
local EarthPressure = pressureAsAtm(101231.656250)
local EarthNitrogenPct = 77.886406
local EarthOxygenPct = 20.892998
local EarthArgonPct = 0.931637
local EarthOrbitalPer = periodAsDay(31558150.649071)
local EarthRotationalPer = periodAsDay(86164.106590)
local EarthTilt = 0.401426 * 180 / math.pi
local EarthEccentricity = 0.016700

if isPlanet(scan) and scan.PlanetClass == "Earthlike body" then
  local starCount = 0 -- this is a naive count, not strictly parent stars.
  for body in bodies(system) do
    if isStar(body) then
      starCount = starCount + 1
    end
  end
  if (starCount == 0) then starCount = 1 end -- there needs to be at least 1 star. Nav beacon scans may send bodies out of order.

  local score = 0
  local gravityFactor = (gravityAsG(scan.SurfaceGravity) - EarthG) / EarthG
  score = score + WeightedScore(gravityFactor, 25, 20)

  local tempFactor = (scan.SurfaceTemperature - EarthTemp) / EarthTemp
  score = score + WeightedScore(tempFactor, 2, 1)

  local surfPressure = pressureAsAtm(scan.SurfacePressure)
  local pressureFactor = (surfPressure - EarthPressure) / EarthPressure
  score = score + WeightedScore(pressureFactor, 1, 2)

  local oxygenPPFactor = -1 -- not present
  local nitrogenPPFactor = -1 -- not present.
  local argonPPFactor = -1 -- not present.
  for atmoMat in materials(scan.AtmosphereComposition) do
    if atmoMat.name == "Nitrogen" then
      nitrogenPPFactor = ((surfPressure * atmoMat.percent) - (EarthPressure * EarthNitrogenPct)) / (EarthPressure * EarthNitrogenPct)
    elseif atmoMat.name == "Oxygen" then
      oxygenPPFactor = ((surfPressure * atmoMat.percent) - (EarthPressure * EarthOxygenPct)) / (EarthPressure * EarthOxygenPct)
    elseif atmoMat.name == "Argon" then
      argonPPFactor = ((surfPressure * atmoMat.percent) - (EarthPressure * EarthArgonPct)) / (EarthPressure * EarthArgonPct)
    end
  end
  score = score + WeightedScore(nitrogenPPFactor, 1, 1)
  score = score + WeightedScore(oxygenPPFactor, 3, 5)
  score = score + WeightedScore(argonPPFactor, 1, 1)

  --- The next three can have negative values to begin with. We really only want to look at absolute differences.
  local orbitalPeriodFactor = (math.abs(periodAsDay(scan.OrbitalPeriod)) - EarthOrbitalPer) / EarthOrbitalPer
  score = score + WeightedScore(orbitalPeriodFactor, 1, 1)

  local rotationPeriodFactor = (math.abs(periodAsDay(scan.RotationPeriod)) - EarthRotationalPer) / EarthRotationalPer
  score = score + WeightedScore(rotationPeriodFactor, 10, 15)

  local axialTiltFactor = (math.abs(scan.AxialTilt * 180 / math.pi) - EarthTilt) / EarthTilt
  score = score + WeightedScore(axialTiltFactor, 1, 1)

  local eccentricityFactor = (scan.Eccentricity - EarthEccentricity) / EarthEccentricity
  score = score + WeightedScore(eccentricityFactor, 20, 0)

  if (scan.TidalLock) then
    score = score + WeightedScore(1, 5, 0)
  end

  -- TODO: This is hard to count in custom criteria.
  --local moonFactor =
  --score = score + WeightedScore(moonFactor, 5, 20)

  local starFactor = (starCount - 1) / 1
  score = score + WeightedScore(starFactor, 5, 0)

  -- Lower score is better. Earth itself should score 0.0
  local extDetails = string.format("Score: %.2f", score)
  --local extDetails = string.format("score: %.2f; g: %.2f; t: %.2f; p: %.2f; sp: %.2f; Oxp: %.2f; Np: %.2f; Ap: %.2f; op: %.2f; rp: %.2f; at: %.2f; ecc: %.2f; star: %.2f",
  --    score, gravityFactor, tempFactor, pressureFactor, surfPressure, oxygenPPFactor, nitrogenPPFactor, orbitalPeriodFactor, argonPPFactor, rotationPeriodFactor, axialTiltFactor, eccentricityFactor, starFactor)
  return true, "ELW Similarity Score", extDetails
end
---@End

 

[Alkibiades]

Reading logs from 1.1.2020 to today I got this one:

Thaileia OS-K c24-8 3 Score: 10,58

EDSM - Elite Dangerous Star Map

The Galactic Positioning System of Elite: Dangerous at your service.

www.edsm.net

 

[marx]

Thanks! I installed it, ran through my log files, and while looking at the scores, I noticed something interesting: all of the high-scoring ones had higher-than-would-be-expected temperatures because of water in their atmospheres. For some reason, in ED water acts as a significantly more potent greenhouse gas than it does in real life - it's most likely an oversimplification, because it needn't be modelled in the game in that much detail.

Also, some below 10, water vapour everywhere: Noijo AN-H c11-20 6 has a score of 7.26, Gludgaa RO-X c28-6 B 4 has 7.64 (A 5 in the same system is 30.78), Lagoon Sector BQ-Y d84 5 has 8.35, Blinking Sector EW-W d1-16 C 9 has 8.36 (love these two names), Screakai GR-W d1-788 has 8.49, Juenae WV-C d1475 has 8.75, Eos Bre MH-M d7-3473 BC 8 has 9.79.

 

[Disemboweled Ego]

I had a similar idea, but with mars (as it is currently, not without the terraforming in Elite) to try to find the most Mars-like planet to land on to see how well that lines up. Never got around to it but this might be useful for that too.

For that and most other actual habitability stuff that would be more important for earth likes the star/distance to star more importantly the effective light/radiation hitting the planet would be the most important factor, that requires some actual calculations based on what the star(s) output.

 

[Cmdr Coddiwompler]

After a discussion with Eahlstan on the discord, I've updated the script above to use absolute values on things like orbital and rotational period and Axial Tilt be cause they can be negative or positive and we really only care about the absolute values, not the direction of orbit, rotation or tilt. So cases like my best example there improved by a bit because it had a slightly negative axial tilt. So grab an update from the post above and re-run!

That said, thoughts on the weights I added?

• Tidal lock: Weight is 5 if if locked, 0 if unlocked
  • Should the weight be scaled based on the delta between orbital and rotational periods?
• Argon: Started with conservative weights of 1 for higher and lower relative values.
• Eccentricity: lower values (ie. more circular) have no weight/bearing as the range so small, it is effectively no difference, but higher values (more elliptical) I put a fairly heavy weight of 20 because that will have a significant impact on seasons and thus on life on that body.

@Disemboweled Ego Yes this could be used to compare to mars as well. Most of the reference values are extracted to variables so just updating those in a separate copy would likely do the trick. But I could also do some refactoring to make this a function which you call and pass in the scan and reference body from two simple criteria functions.

 

[marx]

After testing, looks good to me. I suppose you could scale that weight, but I wonder if there's even a need: as far as I checked, none of those ELWs get a good score anyway. Argon however... that's a good question. I'm rather uncertain of that. Are there any examples of otherwise-high-scoring ELWs having argon in their atmospheres?

Just a side note though, not as something to include in a calculated score: it occurred to me that being a shepherd moon might be problematic, if the parent gas giant's magnetosphere goes out to it. It would depend on a lot of factors though, and it's not something we could model ourselves in ED - just a passing thought.

 

[Cmdr Coddiwompler]

That said, I've overhauled it and created a more generic version (in which one could add multiple reference systems; I've added Mars as a second example and to do this I now support checking Water as another atmospheric component). There's opportunity for a body to have water (or some other material) and not argon -- that difference should be reflected in the score but previously was not (which is probably why water atmos were scoring higher). This difference now captured (albeit at a flat score impact of 1, presently -- do you think 1 is enough for the mismatch?) and so some previous scores may change as a result of this change.

Looking at Sol, Mars and Earth each have a similarity score of 0.0 relative to themselves (ie. the unit tests pass).

I think there were a couple bugfixes. Take a look! (Attached as a text file.)

Moons are still not handled in this version.

 

[Cmdr Coddiwompler]

I'm thinking about this a little more again as I work on implementing this in something other than a custom criteria where I can look at the system as a whole. Other significant factors I could include:

• Number of parent stars or barycentre (should I care about other non-parent stars in the system)?
• If the ELW is a moon or not (ie. non-star parent)
• If the ELW is in a binary/complex orbit with other bodies.
• Maybe the type of the star, but perhaps more generically (as @Disemboweled Ego suggested above), maybe any main sequence star with a similar "apparent brightness"? (Of course, this might into some gnarly orbital mechanics as it depends on the distance from the star, but since earth has a "simple" orbit and a single star, if the comparable has multiple parent stars or is a moon and/or has a complex orbit, I could apply constant differential factors instead.) More "exotic" stars like WD, Neutrons, BHs and most protostars would effectively be uninhabitable and could be given constant high scores.
• Relative number of moons
• Relative distance and mass of the first moon (if present)?
• Someone also mentioned the presence of GGs in the system for collecting asteroids.

What do you think? Which are worth including? Which are not? Anything else worth adding?

Thanks!

 

[marx]

I'm thinking about this a little more again as I work on implementing this in something other than a custom criteria where I can look at the system as a whole. Other significant factors I could include:

• Number of parent stars or barycentre (should I care about other non-parent stars in the system)?
• If the ELW is a moon or not (ie. non-star parent)
• If the ELW is in a binary/complex orbit with other bodies.
• Maybe the type of the star, but perhaps more generically (as @Disemboweled Ego suggested above), maybe any main sequence star with a similar "apparent brightness"? (Of course, this might into some gnarly orbital mechanics as it depends on the distance from the star, but since earth has a "simple" orbit and a single star, if the comparable has multiple parent stars or is a moon and/or has a complex orbit, I could apply constant differential factors instead.) More "exotic" stars like WD, Neutrons, BHs and most protostars would effectively be uninhabitable and could be given constant high scores.
• Relative number of moons
• Relative distance and mass of the first moon (if present)?
• Someone also mentioned the presence of GGs in the system for collecting asteroids.

What do you think? Which are worth including? Which are not? Anything else worth adding?

Thanks!

The thing is, when you look at the system as a whole, you're pretty much moving from "how close to Earth is your ELW" to "how close to the Solar system is your system". Which is fine, but it's not the same original goal anymore.

In my opinion, if you aren't moving to that new goal, then some of these might be overcomplicating things. Are they really needed? If you experiment with them, do they make any significant differences? Should historical events and possibilities like gas giants capturing asteroids count? Would the aspects mentioned above change the daily life of humans down on the surface? (In that case though, Earth's score might be really low at present, since it has a Thargoid Titan in orbit )
But if it they do, then it's not overcomplicating things.