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).

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    $\begingroup$ See the plot in astronomy.stackexchange.com/questions/8440/… for the potential design of a metric to determine what is terrestrial. Only works if you have the mass and radius though. $\endgroup$
    – ProfRob
    Aug 29, 2022 at 14:40
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    $\begingroup$ 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!? $\endgroup$ Aug 30, 2022 at 13:26
  • $\begingroup$ 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. $\endgroup$
    – ProfRob
    Aug 30, 2022 at 14:18

1 Answer 1


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), 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

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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