<p>One way of trying to do this is to plot a surface gravity versus mass plot. It's basically difficult for gas giant planets to hang onto a gaseous envelope without having a high surface gravity.</p>
<p>This plot appeared in <a href="https://arxiv.org/abs/1604.07725" rel="noreferrer">Ballasteros &amp; Luque (2016)</a>, which shows the basic idea. The &quot;terrestrial planets&quot;, icy planets and gas giants appear on different loci in this plot. There are few exoplanets that can be placed in the terrestrial part (or there weren't in 2016 anyway) because you need a mass and radius measurement to calculate the surface gravity.</p>
<p><a href="https://i.sstatic.net/78tpQ.png" rel="noreferrer"><img src="https://i.sstatic.net/78tpQ.png" alt="From Ballesteros &amp; Luque (2016) - a surface gravity vs mass plot" /></a></p>
<p>To use this plot, get the mass and surface gravity (in multiples of Earth gravity and mass) and see which &quot;branch&quot; the object lies closest to.</p>

CC BY-SA 4.0
2022-08-30T14:35:15.203Z
2022-08-30T14:35:15.203Z
ProfRob
<p>NASA exoplanet archive, open exoplanet catalog and exoplanet.eu are some of the most famous catalog of exoplanet discovered by all techniques. However, all of these catalogs are missing the terrestrial flag column, i.e., whether an exoplanet is terrestrial or not.</p>
<p>NASA has its own exoplanet database where it lists 188 terrestrial exoplanets but it's not downloadable like NASA's exoplanet archive. Also, many others have their own habitable zone exoplanet catalog but it includes many less than 188.</p>
<p>My question is can we calculate/answer if an exoplanet is terrestrial or not from all the data given, let's say in NASA exoplanet archive? Or is determining terrestriality completely a different field? Lastly, can we download the NASA terrestrial exoplanet catalog in any way? (I know I can scrape the data using python but I am looking for some prepared csv, if possible).</p>

CC BY-SA 4.0
2022-08-29T14:40:57.533Z
See the plot in https://astronomy.stackexchange.com/questions/8440/maximum-and-minimum-gas-giant-ice-giant-densities for the potential design of a metric to determine what is terrestrial. Only works if you have the mass and radius though.
ProfRob
CC BY-SA 4.0
2022-08-30T13:26:35.700Z
So, it is all about density! I wonder what prevents the existence of gas or ice planets with mass and size similar to Earth. Gravity!?
Abdul Muhaymin -Free Palestine
CC BY-SA 4.0
2022-08-30T14:18:51.597Z
It has nothing to do with density directly. Gas giant planets and terrestrial planets can have the same density. Gas giants have much larger mass. Indeed surface gravity is a much better discriminator. Terrestrial planets have low surface gravity.
ProfRob
<exoplanet><extra-terrestrial><terrestrial-planets>
How to know if an exoplanet is terrestrial?
Abdul Muhaymin -Free Palestine
# How to know if an exoplanet is terrestrial?

(Asked by: username_0 on 2022-08-27)

NASA exoplanet archive, open exoplanet catalog and exoplanet.eu are some of the most famous catalog of exoplanet discovered by all techniques. However, all of these catalogs are missing the terrestrial flag column, i.e., whether an exoplanet is terrestrial or not.

NASA has its own exoplanet database where it lists 188 terrestrial exoplanets but it's not downloadable like NASA's exoplanet archive. Also, many others have their own habitable zone exoplanet catalog but it includes many less than 188.

My question is can we calculate/answer if an exoplanet is terrestrial or not from all the data given, let's say in NASA exoplanet archive? Or is determining terrestriality completely a different field? Lastly, can we download the NASA terrestrial exoplanet catalog in any way? (I know I can scrape the data using python but I am looking for some prepared csv, if possible).

**Tags:** exoplanet, extra-terrestrial, terrestrial-planets
> **Comments:**
> **username_1**: See the plot in https://astronomy.stackexchange.com/questions/8440/maximum-and-minimum-gas-giant-ice-giant-densities for the potential design of a metric to determine what is terrestrial. Only works if you have the mass and radius though.  
> **username_0**: So, it is all about density! I wonder what prevents the existence of gas or ice planets with mass and size similar to Earth. Gravity!?  
> **username_1**: It has nothing to do with density directly. Gas giant planets and terrestrial planets can have the same density. Gas giants have much larger mass. Indeed surface gravity is a much better discriminator. Terrestrial planets have low surface gravity.  

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## 1 answers

### Answer by username_1 on 2022-08-30. Score: 5

One way of trying to do this is to plot a surface gravity versus mass plot. It's basically difficult for gas giant planets to hang onto a gaseous envelope without having a high surface gravity.

This plot appeared in [Ballasteros & Luque (2016)](https://arxiv.org/abs/1604.07725), which shows the basic idea. The "terrestrial planets", icy planets and gas giants appear on different loci in this plot. There are few exoplanets that can be placed in the terrestrial part (or there weren't in 2016 anyway) because you need a mass and radius measurement to calculate the surface gravity.

[![From Ballesteros & Luque (2016) - a surface gravity vs mass plot](https://i.sstatic.net/78tpQ.png)](https://i.sstatic.net/78tpQ.png)

To use this plot, get the mass and surface gravity (in multiples of Earth gravity and mass) and see which "branch" the object lies closest to.


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