Devilish source of dust in atmosphere of Earth and Mars

European Planetary Science Congress 2017 Press Notice
Monday, 18th September

Devilish source of dust in atmosphere of Earth and Mars

Swirling columns of sand and dust, known as dust devils, are a feature of desert areas on Mars and on Earth. Now, a study of terrestrial dust devils has shown that around two thirds of the fine particles lifted by these vortices can remain suspended in the atmosphere and be transported around the globe. The findings have implications for the climate and weather of both planets and, potentially, human health here on Earth. Results will be presented by Dr Jan Raack of the Open University at the European Planetary Science Congress (EPSC) 2017 in Riga, Latvia on Monday, 18th September 2017.

The study by Raack and an international team of collaborators gives important insights into the contribution of dust devils to mineral aerosols in planetary atmospheres. About half of the dust lifted into the martian atmosphere each year is thought to come from dust devils. However, to date, the structure of these vortices has not been well understood. As terrestrial dust devils act very similarly to those on Mars, Raack and colleagues have carried out multiple field campaigns over the past five years to study dust devils in three different deserts on Earth, in China, Morocco and the USA. The researchers took samples of grains lifted by dust devils at different heights, studied tracks left by dust devils on the surface and measured physical and meteorological properties of dust devils.

Raack explains: “The method for sampling is simple – although not actually that pleasant to carry out as it involves getting sandblasted. Essentially, we cover a 5-metre aluminium pipe with double sided sticky tape and run into an active dust devil. We hold the boom upright in the path of a dust devil and wait until the dust devil passes over the boom. Numerous grains are collected on the sticky tape, which are preserved on-site by pressing sections of the tape from different heights onto glass slides.”

Back in the lab, the glass slides are analysed under an optical microscope and all grains measured and counted to gain detailed relative grain size distributions of the sampled dust devils. The results presented at EPSC 2017 focus on samples taken during field campaigns in the south and southwest of Morocco, funded by Europlanet and supported by the Ibn Battuta Centre in Marrakesh.

“We found that the dust devils we measured have a very similar structure, despite different strengths and dimensions. The size distribution of particles within the dust devils seems to correspond to the distribution of grain sizes in the surface they passed over. We have been able to confirm the presence of a sand-skirt – the bottom part of the dust devil with high concentration of larger sand grains – and most particles were only lifted within the first metre. However, the decrease in grain diameter with height is nearly exponential,” says Raack.

In the terrestrial dust devils, the team found that around 60-70% of all the fine dust particles (with diameters up to three hundredths of a millimetre) appear to stay in suspension. These small mineral aerosols can be transported over long distances on Earth and have an influence on the climate and weather. They can also reach populated areas, affecting air quality and human health. On arid Mars, where most of the surface is desert-like and the dust content is much higher, the impact is even larger.

Further analysis of the datasets will include meteorological measurements of the dust devils that will be used to interpret data obtained by landers and rovers on Mars, including the Curiosity rover and the upcoming ExoMars and InSight lander missions.

Further Information

EPSC 2017 abstract: In Situ Sampling of Terrestrial Dust Devils and Implications for Mars, J. Raack, D. Reiss, M.R. Balme, K. Taj-Eddine and G.G. Ori: http://meetingorganizer.copernicus.org/EPSC2017/EPSC2017-13.pdf

EPSC 2017 abstract: In situ measurements of dust devil pressure drop magnitudes and vertical wind speeds, D. Reiss and J. Raack: http://meetingorganizer.copernicus.org/EPSC2017/EPSC2017-451-3.pdf

The results are also published in Astrobiology and are available online as open access (Jan Raack, Dennis Reiss, Matthew R. Balme, Kamal Taj-Eddine, Gian Gabrielle Ori (2017) In Situ Sampling of Relative Dust Devil Particle Loads and Their Vertical Grain Size Distributions. Astrobiology 17, ahead of print, doi:10.1089/ast.2016.1544).
http://online.liebertpub.com/doi/pdf/10.1089/ast.2016.1544

Images

Fig. 1: Sampling a dust devil during field campaign ‘Morocco 2012’. Results of the sampling of this dust devil are presented in Raack et al. (2017) Astrobiology, as well as in the EPSC abstract #13. Image from Raack et al., 2017. Credit: Jan Raack/Dennis Reiss.

Fig. 2: Sampling another dust devil during field campaign ‘Morocco 2012’. This dust devil was not analysed. Credit: Jan Raack/Dennis Reiss.

Fig. 3: Sampling of a dust devil during field campaign ‘Morocco 2016’. The samples are still under analyses. Credit: Jan Raack/Dennis Reiss.

Fig. 4: Another three samplings of dust devils during field campaign ‘Morocco 2016’. Also these samples will be analysed soon. Credit: Jan Raack/Dennis Reiss.

Fig. 5: Chasing a dust devil with the sampling boom during field campaign ‘Morocco 2016’. Credit: Jan Raack/Dennis Reiss.

Fig. 6: Very distinct dust devil at some distance during field campaign ‘Morocco 2016’. Credit: Jan Raack/Dennis Reiss.

Fig. 7: Very large and intensive dust devil in some distance during field campaign ‘Morocco 2016’. Note the camels (small dark dots…) right next to the dust devil for scale. Credit: Jan Raack/Dennis Reiss.

Fig. 8: Same dust devil as in Fig. 7. Note the large dust plume the dust devil leaves in the atmosphere. Credit: Jan Raack/Dennis Reiss.

Fig. 9: Waiting for a dust devil can take some time, even some hours. Credit: Jan Raack/Dennis Reiss.

Fig. 10: The bivouac the team stayed in during the field campaign ‘Morocco 2012’. Credit: Jan Raack/Dennis Reiss.

Fig. 11: Investigating the soil dust devils move over during field campaign ‘Morocco 2012’. Credit: Jan Raack/Dennis Reiss.

Fig. 12: Dust devils can even have some influence on the traffic, therefore drivers should be take extra care when driving through some regions where dust devils are common. The picture shows Dennis Reiss next to a dust devil traffic sign. The image was taken during field campaign ‘Morocco 2016’. Credit: Jan Raack/Dennis Reiss.

Fig. 13: Our meteorological instruments (five stations with 10 different instruments each) on the ground are waiting for some dust devils, while my colleague Dennis Reiss calibrate the position of them via GPS. First results of some of these instruments will be presented at the EPSC (abstract #451). The image was taken during field campaign ‘Morocco 2016’. Credit: Jan Raack/Dennis Reiss.

Fig. 14: Collect some water from a well right in the desert during field campaign ‘Morocco 2012’. Credit: Jan Raack/Dennis Reiss.

Fig. 15: Animation of sampling a very small and weak dust devil during field campaign ‘Morocco 2016’. Samples will be analysed soon. Credit: Jan Raack/Dennis Reiss.

Fig. 16: Animation of Dr Jan Raack running to a dust devil and successful sampling of it during field campaign ‘Morocco 2016’. Samples will be analysed soon. Credit: Jan Raack/Dennis Reiss.

Fig. 17: Animation of a dust devil which directly crosses one of our meteorological stations. Some analyses of this dust devil crossing is presented in EPSC abstract #451. Images were taken during field campaign ‘Morocco 2016’. Credit: Jan Raack/Dennis Reiss.

Fig. 18: Animation of a larger and stronger dust devil who bowl down the team’s GoPro Camera on a tripod. Images were taken during field campaign ‘Morocco 2016’. Credit: Jan Raack/Dennis Reiss.

Fig. 19: Animation of the same dust devil as in Fig. 18, but in real time (1 second per image). Credit: Jan Raack/Dennis Reiss.

Science Contacts
Dr Jan Raack
Marie Skłodowska-Curie Research Fellow
School of Physical Sciences
The Open University
Milton Keynes, UK
jan.raack@open.ac.uk

Media Contacts
Anita Heward
EPSC 2017 Press Officer
+44 07756 034243
anita.heward@europlanet-eu.org

Livia Giacomini
EPSC 2017 Press Officer
livia.giacomini@europlanet-eu.org

Notes for Editors

EPSC 2017
The European Planetary Science Congress (EPSC) 2017 (www.epsc2017.eu) is taking place at the Radisson Blu Latvija in Riga, from Sunday 17 to Friday 22 September 2017. EPSC is the major European annual meeting on planetary science and in 2017 is hosted for the first time in the Baltic States. Around 800 scientists from Europe and around the world will attend the meeting and will give around 1,000 oral and poster presentations about the latest results on our own Solar System and planets orbiting other stars.

EPSC 2017 is organised by Europlanet and Copernicus Meetings. The Local Organising Committee is led by Baltics in Space, a not-for-profit organisation that is supporting 25 members centred around nine Baltic space facilities for the conference. The meeting is sponsored by Investment and Development Agency of Latvia, the Latvian Ministry of Education and Science, Latvijas Mobilais Telefons, Finnish Meteorological Institute, The Estonia-Latvia programme, The Representation of the European Commission in Latvia, the Planetary Science Institute, Latvijas Universitate and The Division for Planetary Sciences of the AAS.

Details of the Congress and a full schedule of EPSC 2017 scientific sessions and events can be found at the official website:
http://www.epsc2017.eu/

Europlanet
Since 2005, the Europlanet project has provided European’s planetary science community with a platform to exchange ideas and personnel, share research tools, data and facilities, define key science goals for the future and engage stakeholders, policy makers and European Citizens with planetary science. Europlanet is the parent organisation of the European Planetary Science Congress (EPSC), and the EPSC Executive Committee is drawn from its membership.

The Europlanet 2020 Research Infrastructure (RI) is a €9.95 million project to address key scientific and technological challenges facing modern planetary science by providing open access to state-of-the-art data, models and facilities across the European Research Area. The project was launched on 1st September 2015 and has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 654208. Europlanet 2020 RI is led by the Open University, UK, and has 33 beneficiary institutions from 19 European countries.
Project website: www.europlanet-2020-ri.eu
Outreach website: www.europlanet-eu.org
Follow @europlanetmedia

Baltics in Space
The philosophy of the nonprofit organization, Baltics in Space, is to “Inventory, Identify, and Integrate” with a sprinkling of Inspiration to build a space product greater than the sum of its parts. The best resource in the space business is people. With an eye to strengthening the triple helix links (Industry, Education, Research), its planned outcomes are integrating Baltic-wide space events, compiling catalogs of skill-sets for prospective users and Baltic space project development with distributed teams and Baltic space education.
http://www.balticsinspace.eu