# Why does Jupiter atmosphere does not get thinner on edges

Looking at Jupiter image the atmosphere edge of planet is very sharp as if it has solid surface which is not as it’s gases giant and there should be some thinning of atmosphere like we see around earth . Or there and could be seen on higher resolution images?

Why does Jupiter's atmosphere not get thinner at the edges?

Looking at an image of the atmosphere's edge it is very sharp as if it has a solid surface, which it has not since it’s a gas giant. There should be some thinning of the atmosphere like we see around Earth. Would this be seen on higher resolution images?

When you look at a spherical object from a distance it appears round, sometimes when you view it from close up it doesn't appear quite so smooth (or round). The wavelength that you look at an object with also affects what you are able to see.

$$\scriptsize \text{Figure 6. High resolution SEM image of CN ball bearing inner ring fabricated from 52100 steel showing} \\ \scriptsize \text{fine globular cementite. Presence of fine precipitates of carbides and nitrides uniformly aggregated in the} \\ \scriptsize \text{fine martensitic microstructure, which act as obstacles to the motion of dislocations.}$$

The above scanning electron microscope image of a smoothly ground ball bearing illustrates this, from a relatively far distance it appears smooth; from much closer the particles constituting its makeup become visible. Image Source: "Effect of Carbonitriding on Endurance Life of Ball Bearing Produced from SAE 52100 Bearing Steels", by Karthikeyan Rajan, Vinod Joshi, and Arindam Ghosh.

A similar principle applies to viewing Jupiter from so far away. While its clouds are far greater than 2000 km thick most of the gases are opaque thus not allowing you to see very far into the atmosphere using visible light.

1. The upper left image shows Jupiter from a distance using visible light. Source: "PJ14 Image 26 - Hot Spot (Enhanced)".

2. The upper right image shows the different layers of Jupiter's atmosphere. Source: "How deep is the atmosphere?".

3. The lower left image from NASA's Juno spacecraft approaching Jupiter on Aug. 27, 2016, the Jovian Infrared Auroral Mapper (JIRAM) instrument captured the planet's glow in infrared light. Source: "Juno Captures Jupiter's Glow in Infrared Light".

4. The last two images are from: "NASA's Juno Mission Provides Infrared Tour of Jupiter's North Pole", there is also a close-up video flythrough of the atmosphere created from infrared imaging. A second video on that webpage, titled: "Jupiter's Dynamo", shows magnetometer imaging overlaid on visible spectrum imaging. The YouTube links for those videos are: "Low 3-D Flyover of Jupiter’s North Pole in Infrared" and "Jupiter's Dynamo".

There certainly is thinning. As the other answer points out, Jupiter is really big, so just about anything else is dwarfed by it's scale.

Scale height can be though of as the distance that the atmospheric density drops by a factor of 1/e, so a few scale heights can be though of as the "thickness" of the atmosphere loosely speaking. It's a loose concept because both temperature and composition can be changing with altitude, it's a good first approximation.

The scale heights of Jupiter and Saturn are in fact much longer than that of Earth's, Wikipedia lists them at about 27 and 60 kilometers, versus Earth's 8 (all rough values). Scale height can be estimated with

$$H = \frac{kT}{Mg}$$

where M is a measure of the masses of the body's atmosphere's constituent molecules, and $g$ is the surface gravity (acceleration) of the body in question. While Jupiter's surface gravity is higher than that of Earth (about 25 m/s^2 versus 9.8 m/s^2), the atmosphere is mostly hydrogen as H2, which per molecule or per mole is fourteen times lighter than Earth's mostly nitrogen as N2.

For the definition of the "edge" of Jupiter, which is somewhat arbitrary, you can read @MarkAdler's excellent answer to the Space SE question "What defines the radius of a ball of gas like Jupiter?"

For a visualization of something similar the ill-defined edge of Saturn's atmosphere (with a scale height double that of Jupiter's) I can steer you to the image in the question Refraction by Saturn's atmosphere - how dense is it here? There are additional links there, but I'l also shown it below, where you can see the appearance of Saturn's rings bend because they are being viewed through its atmosphere.

You can imagine, by the way that the refraction increases closer to the planet that the atmosphere is becoming thicker. There are geometrical effects as well, so this is not a "proof", but only a visual aid.

above: cropped portion of the NASA's Cassini image from here

This tweet from CassiniSaturn shows an image of Saturn's rings being optically distorted by the dense atmosphere. It is explained more fully on this page and is available here.