5 research outputs found
Long-term solar activity influences on South American rivers
River streamflows are excellent climatic indicators since they integrate
precipitation over large areas. Here we follow up on our previous study of the
influence of solar activity on the flow of the Parana River, in South America.
We find that the unusual minimum of solar activity in recent years have a
correlation on very low levels in the Parana's flow, and we report historical
evidence of low water levels during the Little Ice Age. We also study data for
the streamflow of three other rivers (Colorado, San Juan and Atuel), and snow
levels in the Andes. We obtained that, after eliminating the secular trends and
smoothing out the solar cycle, there is a strong positive correlation between
the residuals of both the Sunspot Number and the streamflows, as we obtained
for the Parana. Both results put together imply that higher solar activity
corresponds to larger precipitation, both in summer and in wintertime, not only
in the large basin of the Parana, but also in the Andean region north of the
limit with Patagonia.Comment: Accepted to publication by Journal of Atmospheric and
Solar-Terrestrial Physic
Microbial Fuel Cells Applied to the Metabolically-Based Detection of Extraterrestrial Life
Since the 1970's, when the Viking spacecrafts carried out experiments aimed
to the detection of microbial metabolism on the surface of Mars, the search for
nonspecific methods to detect life in situ has been one of the goals of
astrobiology. It is usually required that the methodology can detect life
independently from its composition or form, and that the chosen biological
signature points to a feature common to all living systems, as the presence of
metabolism. In this paper we evaluate the use of Microbial Fuel Cells (MFCs)
for the detection of microbial life in situ. MFCs are electrochemical devices
originally developed as power electrical sources, and can be described as fuel
cells in which the anode is submerged in a medium that contains microorganisms.
These microorganisms, as part of their metabolic process, oxidize organic
material releasing electrons that contribute to the electric current, which is
therefore proportional to metabolic and other redox processes. We show that
power and current density values measured in MFCs using microorganism cultures
or soil samples in the anode are much larger than those obtained using a medium
free of microorganisms or sterilized soil samples, respectively. In particular,
we found that this is true for extremophiles, usually proposed to live in
extraterrestrial environments. Therefore, our results show that MFCs have the
potential to be used to detect microbial life in situ.Comment: To be published in Astrobiolog
UV habitable zones around M stars
During the last decade, there was a paradigm-shift in order to consider
terrestrial planets within liquid-water habitable zones (LW-HZ) around M stars,
as suitable places for the emergence and evolution of life. Here we analyze the
influence of UV boundary conditions to three planetary systems around dM (HIP
74995, HIP 109388 and HIP 113020). We apply our model of UV habitable zone
(UV-HZ) (Buccino et al. 2006) to these cases and show that during the quiescent
UV output there would not be enough UV radiation within the LW-HZ in order to
trigger biogenic processes. We also analyze the cases of two other M flare
stars and show that the flares of moderate intensity could provide the
necessary energy to trigger those biogenic processes, while the strong flares
not necessary rule-out the possibility of life-bearing planets.Comment: 17 pages, 3 figures, accepted for publication in Icaru
Comparative Survival Analysis of Deinococcus Radiodurans and the Haloarchaea Natrialba Magadii and Haloferax Volcanii, Exposed to Vacuum Ultraviolet Irradiation
The haloarchaea Natrialba magadii and Haloferax volcanii, as well as the
radiation-resistant bacterium Deinococcus radiodurans, were exposed to
vacuum-UV (V-UV) radiation at the Brazilian Synchrotron Light Laboratory
(LNLS). Cell monolayers (containing 105 - 106 cells per sample) were prepared
over polycarbonate filters and irradiated under high vacuum (10-5 Pa) with
polychromatic synchrotron radiation. N. magadii was remarkably resistant to
high vacuum with a survival fraction of ((3.77 \pm 0.76) x 10-2), larger than
the one of D. radiodurans ((1.13 \pm 0.23) x 10-2). The survival fraction of
the haloarchaea H. volcanii, of ((3.60 \pm 1.80) x 10-4), was much smaller.
Radiation resistance profiles were similar between the haloarchaea and D.
radiodurans for fluencies up to 150 J m-2. For fluencies larger than 150 J m-2
there was a significant decrease in the survival of haloarchaea, and in
particular H. volcanii did not survive. Survival for D. radiodurans was 1%
after exposure to the higher V-UV fluency (1350 J m-2) while N. magadii had a
survival lower than 0.1%. Such survival fractions are discussed regarding the
possibility of interplanetary transfer of viable micro-organisms and the
possible existence of microbial life in extraterrestrial salty environments
such as the planet Mars and the Jupiter's moon Europa. This is the first work
reporting survival of haloarchaea under simulated interplanetary conditions.Comment: Draft version (without figures), Accepted for publication in
Astrobiolog