---
title: "“Mini-Neptune” Exoplanets May Actually Be Covered in Radioactive Oceans"
description: "A class of exoplanets thought to resemble gas giants like Neptune may actually be rocky worlds covered in thick, heavily irradiated oceans."
date: "2020-07-20"
modified: "2020-07-20"
authors:
  - name: "Dan Robitzski"
    link: "https://futurism.com/authors/danrobitzski"
url: "https://futurism.com/the-byte/mini-neptune-exoplanets-may-actually-be-covered-in-radioactive-oceans"
categories:
  - "Astronomy"
  - "Exoplanets"
  - "Science & Energy"
  - "Space"
tags:
  - "Exoplanets"
  - "space"
  - "the digest"
---

# “Mini-Neptune” Exoplanets May Actually Be Covered in Radioactive Oceans

![A class of exoplanets thought to resemble gas giants like Neptune may actually be rocky worlds covered in thick, heavily irradiated oceans.](<https://futurism.com/wp-content/uploads/2020/07/mini-neptune-exoplanets-may-actually-be-covered-in-radioactive-oceans.jpg>)
*\<em\>Image: Merikanto/Victor Tangermann\</em\>*

## Nuka-Nepta

New research suggests that astronomers may have been entirely wrong about a class of exoplanets that they call "mini-Neptunes."

These worlds, which were thought to be smaller versions — just 2.4 Earth radii across — of gas giants like Neptune, may actually be rocky exoplanets covered by thick, deeply-irradiated oceans, [according to research](<https://www.sciencedaily.com/releases/2020/07/200720101806.htm>) by scientists at the Laboratoire d'Astrophysique de Marseille. The study, [published last month](<https://iopscience.iop.org/article/10.3847/2041-8213/ab9530>) in *The Astrophysical Journal Letters*, threatens to break down the barriers between two classes of exoplanets that astronomers previously thought were totally separate.

## Totally Rad

[Studying exoplanets](<https://futurism.com/the-byte/nasa-incredible-map-4000-exoplanets>) tends to involve a little bit of trickery. Researchers use various imaging techniques to figure out things like a world's density, chemical composition, and whether it has an atmosphere. In the case of mini-Neptunes, most had assumed that their low density and mass meant they were coated in a thick, gassy atmosphere.

Instead, according to the study, some may have oceans of highly pressurized and heated supercritical liquid that's been irradiated by a powerful greenhouse effect. The ocean, just like a gas giant's atmosphere, could account for the low density and mass of the exoplanets.

## Building Bridges

A [separate study](<https://www.sciencedaily.com/releases/2020/07/200720101806.htm>) published in *Astronomy and Astrophysics* found that the same irradiated oceans could also exist on slightly-smaller, [rocky "super-Earth" exoplanets](<https://futurism.com/astronomers-conclude-massive-exoplanet-host-life>), as their environments are capable of the same powerful greenhouse effect as the mini-Neptunes.

Much of their calculations still need to be tested and verified [through more observations](<https://futurism.com/nasa-telescope-vegetation-exoplanets>) of exoplanets. But if it holds up, the findings suggest that the various worlds out there could be a lot more similar than we thought.

**READ MORE:** [Could mini-Neptunes be irradiated ocean planets?](<https://www.sciencedaily.com/releases/2020/07/200720101806.htm>) \[CNRS\]

**More on exoplanets:** *[Astronomers Discover “Intriguing,” Extremely Earth-Like Exoplanet](<https://futurism.com/astronomers-discover-intriguing-extremely-earth-like-exoplanet>)*

## Author
Dan Robitzki is a senior reporter for Futurism, where he likes to cover AI, tech ethics, and medicine. He spends his extra time fencing and streaming games from Los Angeles, California.

### Author social links  
[Twitter](<https://x.com/danrobitzski>)