Aeolian transport of viable microbial life across the Atacama Desert, Chile: Implications for Mars

Abstract

Here we inspect whether microbial life may disperse using dust transported by wind in the Atacama Desert in northern Chile, a well-known Mars analog model. By setting a simple experiment across the hyperarid core of the Atacama we found that a number of viable bacteria and fungi are in fact able to traverse the driest and most UV irradiated desert on Earth unscathed using wind-transported dust, particularly in the later afternoon hours. This finding suggests that microbial life on Mars, extant or past, may have similarly benefited from aeolian transport to move across the planet and find suitable habitats to thrive and evolve.

Figure 1

Sampling site locations and wind conditions. (A) Map of the Atacama Desert showing the two transects analyzed, Iquique (three sites, I1, I2 and I3) and Tocopilla (T1, T2 and T3). (B) Usual wind flow conditions on the two transects analyzed at 5 PM using the Earth visualization tool (https://earth.nullschool.net/about.html). Blue colors/thinner streamlines show slower winds. Greens and yellows/thicker streamlines show faster winds. The white frame in panel B depicts the zoom detailed in panel A. Note how winds flow north from the Pacific Ocean and then east into the Atacama Desert. Real time conditions may be checked at https://earth.nullschool.net/#current/wind/surface/level/orthographic=-64.85,-23.41,3000.

Figure 2

Dust captured in plates set in the hyperarid core of the Atacama Desert. (A) Mean dust mass captured at the sites inspected of the Iquique transect. (B) Mean dust mass captured at the sites inspected of the Tocopilla transect. Sites 1, 2 and 3 are represented by dark, medium and light gray bars respectively. Means with different letters are statistically different (P < 0.05; two-way ANOVA, Tukey’s post-test, see methods).

Figure 3

Wind vectors of the Atacama transects studied. (A,B), Iquique transect. In (A) wind vectors calculated at 10 AM of August 20 of 2018. In (B), wind vectors at these same sites and date, but at 5 PM. (C,D) Tocopilla transect. In (C) wind vectors calculated at 10 AM of October 27 of 2018, while in (D) the wind vectors at these same sites and date, but at 5 PM. In all panels arrows show the direction of the wind, and different color shading show the wind speed in ms⁻¹ according to the scale show at right. Thin black lines are topographic contours, with the coast drawn as a solid black line. Black stars and numbers below show the studied sites of each transect.

Figure 4

Wind speeds measured at the Tocopilla transect. Wind speeds were measured on October 27 sampling date, with means calculated from twelve measurements. Sites 1, 2 and 3 are represented by dark, medium and light gray bars respectively. Means with different letters are statistically different (P < 0.05; two-way ANOVA, Tukey’s post-test, see methods).

Figure 5

Six hours back trajectories of dust samples at the sites of the transects of the hyperarid core of the Atacama. (A) back trajectories calculated for the sites of the Iquique transect between 4 AM and 10 AM (dark red, dark green and dark blue squares) and between 11 AM and 5 PM (light red, light green and light blue circles) of the August 20 2018 sampling date. (B) back trajectories calculated for the sites of the Tocopilla transect between 4 AM and 10 AM of the October 27 2018 sampling date (dark red, dark green and dark blue squares) and between 11 AM and 5 PM (light red, light green and light blue circles). Thin black lines are topographic contours, with the coast drawn as a solid black line. Black stars and numbers below show the studied sites of each transect.

Figure 6

Microbial isolates identified from dust particles and its distribution at sites of the Iquique transect. Names in bold highlight bacterial species, while light font highlight fungal species.

Figure 7

Microbial isolates identified from dust particles and its distribution at sites of the Tocopilla transect. Species names in bold highlight bacterial species, while light fonts highlight fungal species. Asterisks denote isolates also detected at the Iquique transect.

Figure 8

Main OTUs identified from DNA extracted from dust particles and its distribution at the sites of the Tocopilla transect. Species names in bold highlight bacterial species also detected by cultivation. Values inside site distribution bars indicate percentages of total OTUs.