<p>In the first sols of the Mars 2020 mission the local pressure was something above 750 Pa. It has been decaying since then and <a href="https://mars.nasa.gov/mars2020/weather/" rel="nofollow noreferrer">is now less than 650 Pa</a>, this is what required Ingenuity's rotorblades to rotate faster than originally, for flying. I guess the decay is due to Mars coming closer to the Sun on its more elliptical orbit.</p>
<p>Currently Mars is about half-way between its ap- and perihelion, so if the distance from the Sun is the cause, there could be something around 550 Pa at Perseverance's site during perihelion. Would Ingenuity still be able to fly then? Will the pressure really fall below the triple point of water, and is it due to approaching the Sun? What pressure will eventually be reached and when, before starting to rise? Also, does this happen on the entire planet Mars (the atmosphere getting thinner and eventually thicker again) or are there places on Mars where the local atmospheric pressure is rather constant throughout the Martian year? Did other landers report such rapid pressure changes as well (disregarding a rover's own changing elevation in their course).</p>
<p>Edit: Alright, my question is essentially answered <a href="https://space.stackexchange.com/questions/55077/why-wasnt-the-high-speed-rotation-regime-for-ingenuity-tested-on-earth/55085#55085">by this answer in Space Exploration</a> from &quot;Why not wait?&quot; on.</p>

CC BY-SA 4.0
2021-11-06T23:41:41.593Z
This is an interesting question! In the case of Earth, the seasons are primarily a result of Earth's tilted axis; as it moves around the Sun the southern and northern hemispheres are alternately presented more directly to it, intercepting more sunlight. On the surface we see this as the Sun being high in the sky at noon in one hemisphere while simultaneously low in the sky in the other hemisphere.
uhoh
CC BY-SA 4.0
2021-11-06T23:43:52.993Z
Earth's orbit's eccentricity is small, only about 0.0167 so the distance to the Sun doesn't vary much. *However* Mars's orbit's eccentricity is much larger at 0.0935 so there's more than a 30% yearly variation in insolation in addition to the axial tilt issue. The two hemispheres may turn out to have very different seasonal variations!
uhoh
CC BY-SA 4.0
2021-11-07T06:24:13.073Z
@uhoh Of course, but I'm talking of pressure. The Earth's sea level pressure is a constant ~1 atm (14.7 psi) throughout the year. Mars' more elliptical orbit (0.0935 eccentricity as you say) obviously makes the atmosphere of Mars vary strongly. Is there a place on the red planet where the pressure is more constant like on Earth? The deeper locations perhaps such as Hellas Basin?
LoveForChrist
CC BY-SA 4.0
2021-11-07T06:26:32.110Z
the pressure at sea level changes A LOT! The sea itself will actually rise when there's a low pressure system above it, And the air pressure also changes with temperature, thus the connection to seasons. On Mars the day/night cycle and the seasons determine the temperature and that's the major determining factor of the pressure for any given location.
uhoh
CC BY-SA 4.0
2021-11-07T08:48:49.023Z
@uhoh Really? When pilots set their altimeter to 29.92, altitude 0 always coincides with the sea's surface (except on land that is below sea level such as the Netherlands, there you have a negative altitude), doesn't it? If not, what's the lowest and what's the highest air pressure you'd find on Earth on the beach then?
LoveForChrist
CC BY-SA 4.0
2021-11-07T10:09:47.090Z
Yes, no kidding! [Where can the highest air density be found on Earth?](https://aviation.stackexchange.com/q/30621/14213) See also [low pressure area](https://en.wikipedia.org/wiki/Low-pressure_area) and [high pressure area](https://en.wikipedia.org/wiki/High-pressure_area) **update:** but hey I just learned something! It get so c-c-c-cold when Mars moves furthest from the Sun that a LOT of the CO2 atmosphere freezes into dry ice at both poles, and *that's!* why the pressure drops when it's cold instead of increases! This effect on pressure is even bigger than thermal expansion/contraction!
uhoh
CC BY-SA 4.0
2021-11-07T10:11:47.133Z
See [Local atmospheric pressure and local surface gravity in Jezero crater?](https://space.stackexchange.com/q/51496/12102) and especially the answer to [Why wasn't the high-speed rotation regime for Ingenuity tested on Earth?](https://space.stackexchange.com/q/55077/12102) which links to [Seasonal Variations in Atmospheric Composition as Measured in Gale Crater, Mars](https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019JE006175)
uhoh
CC BY-SA 4.0
2021-11-07T10:11:57.450Z
which says "The atmosphere of Mars is made up of primarily carbon dioxide, and during the Martian year, the barometric pressure is known to cycle up and down substantially as this carbon dioxide freezes out and then is rereleased from polar caps."
uhoh
CC BY-SA 4.0
2021-11-07T10:16:18.010Z
Very good! Thanks @uhoh, the space.SE link answers the question concerning how long the pressure in Jezero crater would remain that low. As for Earth, the pressure at sea level remains _approximately_ constant _if_ we disregard the weather of course, if we assume the weather remains constant throughout the year.
LoveForChrist
CC BY-SA 4.0
2021-11-07T10:17:50.270Z
Please feel free to post an answer to your question! It's always okay to do so. Just a few sentences summarizing what you've found in the post(s) on the other SE site is sufficient. *Thanks!*
uhoh
CC BY-SA 4.0
2021-11-07T10:18:36.330Z
@uhoh Well, actually it's almost a duplicate of the linked one asked by usernumber.
LoveForChrist
CC BY-SA 4.0
2021-11-07T10:20:46.990Z
The Stack Exchange concept of "duplicate" doesn't apply to posts from one SE site to a different SE site. We don't close questions as duplicate of something on a different site. So best way is a short answer explaining a bit here and then linking there, then accepting the answer here. Then people who end up here in the future will see that your question here is answered. It's not a perfect system, but that's what we do.
uhoh
<mars><planetary-atmosphere><weather>
When will Jezero crater on Mars reach its lowest atmospheric pressure and what pressure will that be?
LoveForChrist
# When will Jezero crater on Mars reach its lowest atmospheric pressure and what pressure will that be?

(Asked by: username_0 on 2021-11-06)

In the first sols of the Mars 2020 mission the local pressure was something above 750 Pa. It has been decaying since then and [is now less than 650 Pa](https://mars.nasa.gov/mars2020/weather/), this is what required Ingenuity's rotorblades to rotate faster than originally, for flying. I guess the decay is due to Mars coming closer to the Sun on its more elliptical orbit.

Currently Mars is about half-way between its ap- and perihelion, so if the distance from the Sun is the cause, there could be something around 550 Pa at Perseverance's site during perihelion. Would Ingenuity still be able to fly then? Will the pressure really fall below the triple point of water, and is it due to approaching the Sun? What pressure will eventually be reached and when, before starting to rise? Also, does this happen on the entire planet Mars (the atmosphere getting thinner and eventually thicker again) or are there places on Mars where the local atmospheric pressure is rather constant throughout the Martian year? Did other landers report such rapid pressure changes as well (disregarding a rover's own changing elevation in their course).

Edit: Alright, my question is essentially answered [by this answer in Space Exploration](https://space.stackexchange.com/questions/55077/why-wasnt-the-high-speed-rotation-regime-for-ingenuity-tested-on-earth/55085#55085) from "Why not wait?" on.

**Tags:** mars, planetary-atmosphere, weather
> **Comments:**
> **username_1**: This is an interesting question! In the case of Earth, the seasons are primarily a result of Earth's tilted axis; as it moves around the Sun the southern and northern hemispheres are alternately presented more directly to it, intercepting more sunlight. On the surface we see this as the Sun being high in the sky at noon in one hemisphere while simultaneously low in the sky in the other hemisphere.  
> **username_1**: Earth's orbit's eccentricity is small, only about 0.0167 so the distance to the Sun doesn't vary much. *However* Mars's orbit's eccentricity is much larger at 0.0935 so there's more than a 30% yearly variation in insolation in addition to the axial tilt issue. The two hemispheres may turn out to have very different seasonal variations!  
> **username_0**: @uhoh Of course, but I'm talking of pressure. The Earth's sea level pressure is a constant ~1 atm (14.7 psi) throughout the year. Mars' more elliptical orbit (0.0935 eccentricity as you say) obviously makes the atmosphere of Mars vary strongly. Is there a place on the red planet where the pressure is more constant like on Earth? The deeper locations perhaps such as Hellas Basin?  
> **username_1**: the pressure at sea level changes A LOT! The sea itself will actually rise when there's a low pressure system above it, And the air pressure also changes with temperature, thus the connection to seasons. On Mars the day/night cycle and the seasons determine the temperature and that's the major determining factor of the pressure for any given location.  
> **username_0**: @uhoh Really? When pilots set their altimeter to 29.92, altitude 0 always coincides with the sea's surface (except on land that is below sea level such as the Netherlands, there you have a negative altitude), doesn't it? If not, what's the lowest and what's the highest air pressure you'd find on Earth on the beach then?  
> **username_1**: Yes, no kidding! [Where can the highest air density be found on Earth?](https://aviation.stackexchange.com/q/30621/14213) See also [low pressure area](https://en.wikipedia.org/wiki/Low-pressure_area) and [high pressure area](https://en.wikipedia.org/wiki/High-pressure_area) **update:** but hey I just learned something! It get so c-c-c-cold when Mars moves furthest from the Sun that a LOT of the CO2 atmosphere freezes into dry ice at both poles, and *that's!* why the pressure drops when it's cold instead of increases! This effect on pressure is even bigger than thermal expansion/contraction!  
> **username_1**: See [Local atmospheric pressure and local surface gravity in Jezero crater?](https://space.stackexchange.com/q/51496/12102) and especially the answer to [Why wasn't the high-speed rotation regime for Ingenuity tested on Earth?](https://space.stackexchange.com/q/55077/12102) which links to [Seasonal Variations in Atmospheric Composition as Measured in Gale Crater, Mars](https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019JE006175)  
> **username_1**: which says "The atmosphere of Mars is made up of primarily carbon dioxide, and during the Martian year, the barometric pressure is known to cycle up and down substantially as this carbon dioxide freezes out and then is rereleased from polar caps."  
> **username_0**: Very good! Thanks @uhoh, the space.SE link answers the question concerning how long the pressure in Jezero crater would remain that low. As for Earth, the pressure at sea level remains _approximately_ constant _if_ we disregard the weather of course, if we assume the weather remains constant throughout the year.  
> **username_1**: Please feel free to post an answer to your question! It's always okay to do so. Just a few sentences summarizing what you've found in the post(s) on the other SE site is sufficient. *Thanks!*  
> **username_0**: @uhoh Well, actually it's almost a duplicate of the linked one asked by usernumber.  
> **username_1**: The Stack Exchange concept of "duplicate" doesn't apply to posts from one SE site to a different SE site. We don't close questions as duplicate of something on a different site. So best way is a short answer explaining a bit here and then linking there, then accepting the answer here. Then people who end up here in the future will see that your question here is answered. It's not a perfect system, but that's what we do.  

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