Despite the absence of a global Earth-like magnetic dipole, the Martian atmosphere is well protected from the effects of the solar wind on ion escape from the planet. New research shows this using measurements from the Swedish particle instrument ASPERA-3 on the Mars Express spacecraft. The results have recently been presented in a doctoral thesis by Robin Ramstad, Swedish Institute of Space Physics and Umeå University, Sweden.
Present-day Mars is a cold and dry planet with less than 1% of Earth’s atmospheric pressure at the surface. However many geological features indicate the planet had an active hydrological cycle about 3-4 billion years ago. An active hydrological cycle would have required a warmer climate in the planet’s early history and therefore a thicker atmosphere, one capable of creating a strong greenhouse effect.
Left: Charged particles from the sun (the solar wind) form an induced magnetosphere round Mars, which unlike the sun does not have its own intrinsic magnetic field (artwork: Anastasia Grigoryeva).
Right: Robin Ramstad points out the position of the Swedish instrument ASPERA-3 on a model of the Mars Express spacecraft (photo: Anastasia Grigoryeva)
A common hypothesis maintains that the solar wind over time has eroded the early Martian atmosphere, causing the greenhouse effect, and thus the hydrological cycle, to collapse. Unlike Earth, Mars has no global magnetic dipole, but the solar wind instead induces currents in the ionized upper atmosphere (the ionosphere), creating an induced magnetosphere.
“It has long been thought that this induced magnetosphere is insufficient to protect the Martian atmosphere,” says Robin Ramstad. “However our measurements show something different.”
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.
Robin Ramstad is from from Västerås in Sweden and has a Master of Science degree in Engineering Physics from Luleå University of Technology.
On Friday 8 December 2017 Robin Ramstad of the Swedish Institute of Space Physics in Kiruna and Umeå University will defend his PhD thesis entitled Ion escape from Mars: measurements in the present to understand the past.
The thesis defence will take place at 9 am in the Aula at the Swedish Institute of Space Physics in Kiruna.
The faculty opponent is Assoc. Prof. David Brain, Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, USA. The candidate’s supervisors are Prof. Stas Barabash and Assoc. Prof. Yoshifumi Futaana at the Swedish Institute of Space Physics, Kiruna.
Robin Ramstad, Swedish Institute of Space Physics, email@example.com, tel. +46-980-79115
Rick McGregor, Information Officer, Swedish Institute of Space Physics, firstname.lastname@example.org, tel. +46-980-79178
Information about the defence and a link to the thesis: http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-141892
IRF’s Mars Express web page: http://www.irf.se/link/MEX_press
AGU Editor’s Highlight of Robin Ramstad’s GRL paper: https://eos.org/editor-highlights/where-did-the-water-go-on-mars
Rick McGregor | idw - Informationsdienst Wissenschaft
Do ice cores help to unravel the clouds of climate history?
21.06.2019 | Leibniz Institute for Tropospheric Research (TROPOS)
News from the diamond nursery
21.06.2019 | Goethe-Universität Frankfurt am Main
From June 25th to 27th 2019, the Fraunhofer Institute for Digital Media Technology IDMT in Ilmenau (Germany) will be presenting a new solution for acoustic quality inspection allowing contact-free, non-destructive testing of manufactured parts and components. The method which has reached Technology Readiness Level 6 already, is currently being successfully tested in practical use together with a number of industrial partners.
Reducing machine downtime, manufacturing defects, and excessive scrap
The quality of additively manufactured components depends not only on the manufacturing process, but also on the inline process control. The process control ensures a reliable coating process because it detects deviations from the target geometry immediately. At LASER World of PHOTONICS 2019, the Fraunhofer Institute for Laser Technology ILT will be demonstrating how well bi-directional sensor technology can already be used for Laser Material Deposition (LMD) in combination with commercial optics at booth A2.431.
Fraunhofer ILT has been developing optical sensor technology specifically for production measurement technology for around 10 years. In particular, its »bd-1«...
The well-known representation of chemical elements is just one example of how objects can be arranged and classified
The periodic table of elements that most chemistry books depict is only one special case. This tabular overview of the chemical elements, which goes back to...
Light can be used not only to measure materials’ properties, but also to change them. Especially interesting are those cases in which the function of a material can be modified, such as its ability to conduct electricity or to store information in its magnetic state. A team led by Andrea Cavalleri from the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg used terahertz frequency light pulses to transform a non-ferroelectric material into a ferroelectric one.
Ferroelectricity is a state in which the constituent lattice “looks” in one specific direction, forming a macroscopic electrical polarisation. The ability to...
Researchers at TU Graz calculate the most accurate gravity field determination of the Earth using 1.16 billion satellite measurements. This yields valuable knowledge for climate research.
The Earth’s gravity fluctuates from place to place. Geodesists use this phenomenon to observe geodynamic and climatological processes. Using...
29.04.2019 | Event News
17.04.2019 | Event News
15.04.2019 | Event News
24.06.2019 | Medical Engineering
24.06.2019 | Trade Fair News
24.06.2019 | Life Sciences