Presence of airborne dust could signify increased habitability of
distant planets

Date:
June 9, 2020
Source:
University of Exeter
Summary:
Scientists have expanded our understanding of potentially habitable
planets orbiting distant stars by including a critical climate
component -- the presence of airborne dust.



FULL STORY ========================================================================== Scientists have expanded our understanding of potentially habitable
planets orbiting distant stars by including a critical climate component
-- the presence of airborne dust.


==========================================================================
The researchers suggest that planets with significant airborne dust --
similar to the world portrayed in the classic sci-fi Dune -- could be
habitable over a greater range of distances from their parent star,
therefore increasing the window for planets capable of sustaining life.

The team from the University of Exeter, the Met Office and the University
of East Anglia (UEA) isolated three primary impacts of dust.

Planets orbiting close to stars smaller and cooler than the Sun, so-called
M - - dwarfs, are likely to exist in synchronised rotation-orbit states, resulting in permanent day and night sides.

The researchers found that dust cools down the hotter dayside but also
warms the night side, effectively widening the planet's `habitable
zone', the range of distances from the star where surface water could
exist. Detection and characterisation of potentially habitable distant
planets is currently most effective for these types of worlds.

The results, published today in Nature Communications, also show that for planets in general, cooling by airborne dust could play a significant
role at the inner edge of this habitable zone, where it gets so hot
that planets might lose their surface water and become inhabitable --
in a scenario thought to have occurred on Venus.



==========================================================================
As water is lost from the planet and its oceans shrink, the amount of
dust in the atmosphere can increase and, as a result, cool the planet
down. This process is a so-called negative climate feedback, postponing
the planet's loss of its water.

Crucially, the research also suggests that the presence of dust must be accounted for in the search for key biomarkers indicative of life --
such as the presence of methane -- as it can obscure their signatures
as observed by astronomers.

The experts suggest that these results mean exoplanets must be very
carefully considered before being potentially rejected in the search
for habitable distant worlds.

Dr Ian Boutle, lead author of the study and jointly from the Met Office
and the University of Exeter said:" On Earth and Mars, dust storms have
both cooling and warming effects on the surface, with the cooling effect typically winning out. But these 'synchronised orbit' planets are very different. Here, the dark sides of these planets are in perpetual night,
and the warming effect wins out, whereas on the dayside, the cooling
effect wins out. The effect is to moderate the temperature extremes,
thus making the planet more habitable." The presence of mineral dust
is known to play a substantial role in climate, both regionally as found
on Earth and globally, as experienced on Mars.



==========================================================================
The research team performed a series of simulations of terrestrial or
Earth- sized exoplanets, using state-of-the-art climate models, and
showed for the first time that naturally occurring mineral dust will
have a significant impact on whether exoplanets can support life.

Prof Manoj Joshi from UEA said that this study again shows how the
possibility of exoplanets supporting life depends not only on the
stellar irradiance -- or the amount of light energy from the nearest
star -- but also on the planet's atmospheric make-up. "Airborne dust
is something that might keep planets habitable, but also obscures our
ability to find signs of life on these planets. These effects need to be considered in future research." The research project included part of an undergraduate project by Duncan Lyster, who features on the paper's list
of authors. Duncan, who now runs his own business crafting surfboards
added: "It's exciting to see the results of the practical research
in my final year of study paying off. I was working on a fascinating
exoplanet atmosphere simulation project, and was lucky enough to be part
of a group who could take it on to the level of world-class research."
The quest to identify habitable planets far beyond our solar system is
an integral part of current and future space missions, many focused on answering the question of whether we are alone.

Nathan Mayne, from the University of Exeter, who along with a co-author
was able to work on this project thanks to funding from the Science and Technology Facilities Council (STFC) added: "Research such as this is only possible by crossing disciplines and combing the excellent understanding
and techniques developed to study our own planet's climate, with cutting
edge astrophysics.

"To be able to involve undergraduate physics students in this, and other projects, also provides an excellent opportunity for those studying
with us to directly develop the skills needed in such technical and collaborative projects.

"With game-changing facilities such as the JWST and E-ELT, becoming
available in the near future, and set to provide a huge leap forward in
the study of exoplanets, now is a great time to study Physics!"

========================================================================== Story Source: Materials provided by University_of_Exeter. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Ian A. Boutle, Manoj Joshi, F. Hugo Lambert, Nathan J. Mayne, Duncan
Lyster, James Manners, Robert Ridgway, Krisztian Kohary. Mineral
dust increases the habitability of terrestrial planets but
confounds biomarker detection. Nature Communications, 2020; 11
(1) DOI: 10.1038/s41467-020- 16543-8 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200609111105.htm

--- up 20 weeks, 2 hours, 34 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1337:3/111)