36
Nitrogen, with a molecular mass of 28 atomic mass units, is too light to have remained in Mars's atmosphere. Carbon dioxide, with a molecular mass of 44 amu, could (and does) exist on Mars, but it is rather sparse.
Venus's atmosphere appears to contain a small amount of nitrogen when viewed on a percentage basis. "Only" 3.5% of all of the gases in ...
13
3.5% of all atmosphere in Venus still accounts for more partial pressure of nitrogen than on Earth.
Venus has ~90bar pressure at the surface, 3.5% of them are ~3.2 bar nitrogen. Earth has only 0.8 bar nitrogen. Even accounting for the Venus surface temperature (~700K vs ~300K on Earth), one still gets more nitrogen mass per volume.
Mars:
Most of the ...
11
This is supplementary to antispinward's excellent answer and provides additional sources and a visualization from the JAXA spacecraft Atasuki. It has been shamelessly borrowed from Would it be possible to "ride the wave" on Venus?
The recently published paper in Nature Geoscience Atmospheric mountain wave generation on Venus and its influence on the solid ...
10
This shape is usually known as the "Y feature" and it appears in the ultraviolet (most images of the Venusian atmosphere incorporate information from the ultraviolet because that provides the most detail).
Peralta et al. (2015), "Venus's major cloud feature as an equatorially trapped wave distorted by the wind" describes the formation of the Y feature in ...
6
As far as I know, "seeing" (or rather the effects influencing optical wave propagation) is caused by turbulence in the atmosphere.
Using the Reynolds number Number $ Re = \dfrac{\rho L v}{\mu}$ as a measure for turbulence:
density $\rho$ drops due to the reduced pressure (about 1/100 earth pressure), additionally the gravity is smaller than on earth
...
5
The main issue is that there is relatively little material in Saturn's atmosphere that can efficiently scatter radar waves, so the radar basically just gets absorbed.
The key point is that it's much harder to get a radar return from the very small objects (aerosol droplets or tiny ice particles) that would make up clouds in Saturn's upper atmosphere than it ...
4
The images you present aren't literal images of Saturn's rings. They're "Doppler-delay" plots: the vertical axis represents distance from Earth, while the horizontal axis represents speed towards or away from Earth. Since the ring particles are moving in circular paths around Saturn, this produces an elliptical chart.
Further evidence that this isn't a ...
3
... so why is this the case?
It may in fact NOT be the case!
Interestingly Phys.org's new item Early Mars was covered in ice sheets, not flowing rivers: study just showed up. It begins:
A large number of the valley networks scarring Mars's surface were carved by water melting beneath glacial ice, not by free-flowing rivers as previously thought, according ...
3
As we haven't measured the atmosphere of many rocky planets yet, there aren't many examples. But I found 55 Cancri e:
It is a super-earth with very close tidally locked orbit and an atmosphere that has been measured by Hubble. A year on the exoplanet lasts for only 18 hours and temperatures on the surface are thought to reach around 2000 degrees Celsius. The ...
2
You asked if we know of any such planets, this raises the question of how sure do you want to be. There are definitely a variety of planets located close to their stars which have atmospheres (hot Jupiters, hot Neptunes, various volatile-rich super-Earths), that have short tidal spindown timescales. These planets are generally assumed to be in a 1:1 spin-...
2
Now that phosphine has probably been discovered in relatively large
quantities in the Venusian atmosphere
It is not large, it's only 20 ppb.
I heard that there have been other unexplained phenomena (i.e. dark
patches) seen.
Yes, dark patches has been observed on Venus from quite a time. Scientist aren't able to figure it out and are speculating to be ...
2
Sure, but it is not straightforward. There's a lot of degeneracies involved, such as many molecules sharing similar absorption bands, the presence of clouds, scattering, absorption happening at many different pressure ranges, solving the chemical equilibirum equations of the species and the temperature-profile modifying the overall spectrum as well.
There's ...
2
What your calculations don't account for is the dynamics of the meterological system. An atmosphere with $10^{18}$kg of water vapour would be a powerful greenhouse, but at the temperatures on Earth, there is no way that the atmosphere could hold so much water vapour, it would rapidly condense.
Instead, in the case of a major impact into the oceans, a lot of ...
1
Current conditions on Mars are between 1mbar and 10mbar with an average around 6mbar atmospheric pressure and surface temperatures between ~70°C and +20°C depending on place and time-of-day and season. The triple point of water is around 0°C and 6mbar pressure.
Thus the triple point of water is within the limits of what you find on Mars today - not ...
1
Frequencies of terrestrial whistlers are 1 kHz to 30 kHz, while radio telescopes work at 30 megahertz to 300 gigahertz.
Radio telescopes would need to be 1000x larger in order to resolve the direction of extraterrestrial whistlers.
1
A recent paper, Way & Del Genio (2020) suggests that a Venus-like planet could have been habitable until the present day thanks to its slow rotation: on slowly-rotating planets, the buildup of reflective clouds over the daylight side of the planet could result in the planet remaining in a habitable state at higher insolations than fast-rotating planets (...
1
Hmm... here's my guess.
Cumulus clouds form due to warm, moist air rising. With the atmosphere of Mars being so cold, there's little heat to facilitate the formation of cumulus clouds. Cirrus clouds, on the other hand, are composed of sparse ice crystals, which makes them probably more common on Mars than cumulus clouds. After all, supercooled water does ...
1
[WARNING: I may be wrong. Astronomy is my hobby and I will answer to the extent that I know of. I may be a bit off.]
Mars' atmosphere contains I guess what you can say 2 major parts. Gases, and debris picked up by winds on the lower levels of the atmosphere (like Earth).
Gases
Mars' atmospheric gas composition mainly consists of CO$_2$.
More ...
Only top voted, non community-wiki answers of a minimum length are eligible
