Leaky atmosphere linked to lightweight planet

Posted: February 9, 2018 by oldbrew in Astrophysics, atmosphere, research, solar system dynamics
Tags: ,

Solar wind at Mars [image credit: universetoday.com]


The researchers say ‘the solar wind likely only had a very small direct effect on the amount of Mars atmosphere that has been lost over time.’ This makes them suspect that ‘a magnetic field is not as important in shielding a planet’s atmosphere as the planet’s gravity itself.’ It was always hard to see how the magnetic shield theory worked when Venus with its dense atmosphere has little magnetism.

The Red Planet’s low gravity and lack of magnetic field makes its outermost atmosphere an easy target to be swept away by the solar wind, but new evidence from ESA’s Mars Express spacecraft shows that the Sun’s radiation may play a surprising role in its escape, reports Phys.org.

Why the atmospheres of the rocky planets in the inner solar system evolved so differently over 4.6 billion years is key to understanding what makes a planet habitable.

While Earth is a life-rich water-world, our smaller neighbour Mars lost much of its atmosphere early in its history, transforming from a warm and wet environment to the cold and arid plains that we observe today. By contrast, Earth’s other neighbour Venus, which although inhospitable today is comparable in size to our own planet, and has a dense atmosphere.

One way that is often thought to help protect a planet’s atmosphere is through an internally generated magnetic field, such as at Earth. The magnetic field deflects charged particles of the solar wind as they stream away from the Sun, carving out a protective ‘bubble’ – the magnetosphere – around the planet.

At Mars and Venus, which don’t generate an internal magnetic field, the main obstacle to the solar wind is the upper atmosphere, or ionosphere. Just as on Earth, solar ultraviolet radiation separates electrons from the atoms and molecules in this region, creating a region of electrically charged – ionised – gas: the ionosphere. At Mars and Venus this ionised layer interacts directly with the solar wind and its magnetic field to create an induced magnetosphere, which acts to slow and divert the solar wind around the planet.

For 14 years, ESA’s Mars Express has been looking at charged ions, such as oxygen and carbon dioxide, flowing out to space in order to better understand the rate at which the atmosphere is escaping the planet.

The study has uncovered a surprising effect, with the Sun’s ultraviolet radiation playing a more important role than previously thought.

“We used to think that the ion escape occurs due to an effective transfer of the solar wind energy through the martian induced magnetic barrier to the ionosphere,” says Robin Ramstad of the Swedish Institute of Space Physics, and lead author of the Mars Express study.

“Perhaps counter-intuitively, what we actually see is that the increased ion production triggered by ultraviolet solar radiation shields the planet’s atmosphere from the energy carried by the solar wind, but very little energy is actually required for the ions to escape by themselves, due to the low gravity binding the atmosphere to Mars.”

Continued here.

Comments
  1. Paul Vaughan says:

    Debate is the problem, NOT the solution.

    The Head of The Western Snake:

    =
    “We used to think that […]”
    “Perhaps counter-intuitively, what we actually see is […]”

    =

    Western “scientific” justice is a major charm offensive administered by academic magicians.

    “Theory is the STAKE. Theoretical “logic” is the tether.”
    https://tallbloke.wordpress.com/suggestions-31/comment-page-1/#comment-133201

  2. Bitter@twisted says:

    Real science here.
    A theory is compared to empirical data and when the data does not fit the theory, the theory is binned.
    Now compare the situation with a currently fashionable, consensus, pseudoscience……

  3. oldbrew says:

    We used to think that the ion escape occurs due to an effective transfer of the solar wind energy through the martian induced magnetic barrier to the ionosphere,” says Robin Ramstad of the Swedish Institute of Space Physics, and lead author of the Mars Express study.

    “Perhaps counter-intuitively, what we actually see is that the increased ion production triggered by ultraviolet solar radiation shields the planet’s atmosphere from the energy carried by the solar wind, but very little energy is actually required for the ions to escape by themselves, due to the low gravity binding the atmosphere to Mars.” [bold added]

    Read more at: http://phys.org/news/2018-02-leaky-atmosphere-linked-lightweight-planet.html

  4. ren says:

    “The ionising nature of the Sun’s radiation is found to produce more ions than can be removed by the solar wind. Although the increased ion production helps to shield the lower atmosphere from the energy carried by the solar wind, the heating of the electrons appears to be sufficient to drag along ions under all conditions, creating a ‘polar wind’. Mars’ weak gravity – about one third that of Earth’s – means the planet cannot hold on to these ions and they readily escape into space, regardless of the extra energy supplied by a strong solar wind.

    At Venus, where the gravity is similar to Earth’s, a lot more energy is required to strip the atmosphere in this way, and ions leaving the sunward side would likely fall back towards the planet on the lee-side unless they are accelerated further.

    “We therefore conclude that in the present day, ion escape from Mars is primarily production-limited, and not energy-limited, whereas at Venus it is likely to be energy-limited given the larger planet’s higher gravity and high rate of ionisation, being nearer to the Sun,” adds Robin.”

    Read more at: https://phys.org/news/2018-02-leaky-atmosphere-linked-lightweight-planet.html#jCp

  5. ren says:

    “The ionosphere, a region in the upper atmosphere between around 50 km and 600 km from Earth. While there are indications that the density of the air in the lower ionosphere relates to geomagnetic activity, the underlying processes are not well understood.

    The ionosphere contains ionised atoms resulting from the effect of ultraviolet light from the Sun. Strong electric currents flow in the sunlit hemisphere, which is much more conductive than the night side.

    In addition to these diurnal variations, magnetic storms resulting from solar activity also cause irregular disturbances in the ionosphere and magnetosphere. For example, the aurora borealis and aurora australis are formed when charged particles in solar wind are channelled by Earth’s magnetic field into the atmosphere near the poles.”

    http://www.esa.int/Our_Activities/Observing_the_Earth/Swarm/Earth_s_external_environment

  6. ren says:

    In a word, UV radiation and ionosphere can be more important to protect the atmosphere than it seems, by absorbing solar wind energy.

  7. oldbrew says:

    NASA’s GOLD mission continues despite launch anomaly
    https://tallbloke.wordpress.com/2018/01/26/nasas-gold-mission-continues-despite-launch-anomaly/

    NASA: GOLD – Mission Overview

    The Global-scale Observations of the Limb and Disk (GOLD) mission will examine the response of the upper atmosphere to forcing from the Sun, the magnetosphere and the lower atmosphere.
    The Global-scale Observations of the Limb and Disk, or GOLD, mission is designed to explore the nearest reaches of space. Capturing never-before-seen images of Earth’s upper atmosphere, GOLD explores in unprecedented detail our space environment — which is home to astronauts, radio signals used to guide airplanes and ships, as well as satellites that provide communications and GPS systems.

    https://www.nasa.gov/content/goddard/gold-mission-overview

  8. JB says:

    https://phys.org/news/2017-12-mars-atmosphere-solar.html#nRlv

    “The Swedish-led ion mass analyser on Mars Express has been measuring the ion escape from Mars since 2004. In his research, Robin Ramstad has combined and compared measurements of the ion escape under varying solar wind conditions and levels of ionizing solar radiation, so-called extreme ultraviolet (EUV) radiation. The results show that the solar wind has a comparatively small effect on the ion escape rate, which instead mainly depends on the EUV radiation. This has a large effect on estimations of the total amount of atmosphere that has escaped to space.

    “Despite stronger solar wind and EUV-radiation levels under the early Sun, ion escape can not explain more than 0.006 bar of atmospheric pressure lost over the course of 3.9 billion years,” says Robin Ramstad. “Even our upper estimate, 0.01 bar, is an insignificant amount in comparison to the atmosphere required to maintain a sufficiently strong greenhouse effect, about 1 bar or more according to climate models.”

    The results presented in the thesis show that a stronger solar wind mainly accelerates particles already escaping the planet’s gravity, but does not increase the ion escape rate. Contrary to previous assumptions, the induced magnetosphere is also shown to protect the bulk of the Martian ionosphere from solar wind energy transfer.”

  9. oldmanK says:

    Some notable comments:

    PV : ““Theory is the STAKE. Theoretical “logic” is the tether.””

    Bitter@twisted says: “A theory is compared to empirical data and when the data does not fit the theory, the theory is binned.” That is not the standard procedure. It is ‘protect the dogma and ignore the empirical’.

    Profs A Nur on geology (in 2016): ” — we seem to have adhered to the totally arbitrary assumption of irrotational crustal deformation. However, there is absolutely no a priori reason to make such a limiting assumption. “

  10. donald penman says:

    It could be that Venus is losing its atmosphere very quickly because of its high surface temperature and being closer to the Sun than the Earth. Both Mars and Venus have a high percentage of CO2 in there atmosphere which may indicate a higher rate of loss of lighter elements in the atmosphere. I wonder if Venus will eventually look like Mars.

  11. p.g.sharrow says:

    Mars is a small version of Earth. Neither is anything like Venus. While Venus is nearly the same size as Earth, they have little in common. Venus could not have originated in it’s present orbit, Everything about it’s rotation and atmosphere is wrong…pg

  12. Damian says:

    “Mars lost much of its atmosphere early in its history, transforming from a warm and wet environment to the cold and arid plains that we observe today.”

    There is no empirical evidence that Mars ever had more of an atmosphere or for it’s warm wet past.

  13. BA2204 says:

    Whereas Venus seems to have a young surface, from massive volcanism. Such would be a good source of CO2. Brett

  14. oldbrew says:

    Olympus Mons stands about two and a half times as tall as Mount Everest’s height above sea level. It is the tallest mountain in the Solar System. It is the youngest of the large volcanoes on Mars, having formed during Mars’s Hesperian Period. It is currently the largest volcano discovered in the Solar System

    http://en.wikipedia.org/wiki/Olympus_Mons

    Research published in June 2010 mapped 40,000 river valleys on Mars, roughly quadrupling the number of river valleys that had previously been identified.

    http://en.wikipedia.org/wiki/Water_on_Mars#Lakes_and_river_valleys

  15. ren says:

    A very strong drop in solar ultraviolet radiation is visible.
    This is due to very low sunspot activity (weak flares).

  16. dscott says:

    Yeah, I’m not buying the whole gravity explanation either.

    Atmospheric Pressure
    Venus at 92 bar,
    Earth at 1 bar
    Titan at 1.5 to 2 bar
    Mars at 7 millibar or .007 bar

    Gravity
    Venus is .98 of earth’s gravity
    Titan is .14 of earth’s gravity
    Mars is .38 of earth’s gravity
    Moon is .1654 of earth’s gravity

    Try again fellas, I’m sure you can scam more grant money from the US govenment

  17. E.M.Smith says:

    In geology, CO2 becomes carbonate. N2 becomes nitrates. O2 becomes oxides. H2O becomes hydrates.

    Atmosphere “leaves” by becoming rock.

    The Earth has more atmosphere than Mars as our nuclear core has not run out of fuel to power our volcanic processes that ‘de-gas’ those rock types above. Carbonates liberate CO2 into lava. Oxides get reduced. Water of hydration boiled out. Nitrates broken down too.

    When our volcanic activity stops (likely in this Billion years) we’ll start to look like Mars too as all our gasses and liquids get turned to various kinds of rocks.

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