Out of This World: From the Bottom of the Red Sea to the Red Planet

The deep-sea brines of the Red Sea are some of the most extreme environments on Earth. They have high salinity, high temperature, high pressure, and no oxygen. Despite such harsh conditions, several organisms still live in these brines. The study of deep-sea brines and their inhabitants has several advantages. In addition to finding several new species, deep-sea brines are a source of useful new molecules produced by these organisms. These new molecules could be used for healing people or even cleaning up our planet. The deep-sea brines could also aid us in looking for extraterrestrial life. These brines are also helpful for planning future space missions due to similarities with conditions on other planets and moons.


WHAT ARE DEEP-SEA BRINES AND HOW ARE THEY FORMED?
The Red Sea is unique! It is growing by a few millimeters every year. In a few million years it will become a full-fledged ocean, like the Atlantic or the Pacific. The Red Sea is growing because of the separation of the Arabian and African tectonic plates. The gap left between these plates,

TECTONIC PLATES
Large pieces of the Earth's crust shifting or moving around, sometimes. Bumping into one another or moving away from each other. which is in the middle of the Red Sea, is filled by patches of new oceanic crust. As oceanic crust is denser than continental crust, these patches create deep spots called deeps (a deeper area or hole in the seafloor) and are scattered across the mid-section of the Red Sea [ ].
The movement of the earth's crust happening under the Red Sea exposes massive buried deposits of salt. The deposits were formed from the drying of a prehistoric ocean that existed in this area. The seawater dissolves some of the salt and becomes a brine, which is very salty water. Salinity, which is the word for the measure of saltiness, can increase by up to -fold in the brines. These brines are heavy, so they concentrate at the bottom of the sea and accumulate in the deeps formed by the oceanic crust. The high density of the brines and their sheltered location in the deeps prevents them from mixing with seawater. Because of this, deep-sea brines are very stable and look like underwater lakes. They even have waves across their surfaces and beaches at their rims. In addition to higher salinity, brines have other di erences from seawater: they have no oxygen and have higher amounts of metals and other elements. Brines also have a lower pH than seawater and a higher temperature.

AN ACCIDENTAL DISCOVERY
Deep-sea brines were accidentally discovered in the s, when researchers collected a deep-sea water sample that was much saltier and warmer than usual. Follow-up surveys discovered at least di erent deep-sea brines scattered across the center of the Red Sea ( Figure ). Each brine is unique due to di erences in local geology, age, and di erences in heating from the earth's crust [ ]. Atlantis II is the biggest (over km ), the hottest ( . • C), and one of the oldest brines. On the other extreme, Kebrit is the smallest ( . km ), the coldest ( . • C), and one of the youngest brines. Kebrit is also rich in sulfur and is very smelly-"kebrit" is the Arabic word for sulfur, which smells like rotten eggs.

WHAT LIVES IN DEEP-SEA BRINES?
For a long time, researchers thought that conditions in the deep-sea brines were too extreme for life. They assumed that no organisms would be able to survive there. However, technical advances, particularly in molecular biology, allowed us to explore the brines

MOLECULAR BIOLOGY
The study of living things based on their molecules (such as DNA or proteins) rather than the whole organism. in more detail and revealed thriving communities. Studies have found microbes, animals, and even viruses in the brines [ ]. These studies have discovered many new species, some unlike any other on our planet ( Figure ). These organisms are so unique that some of these findings are equivalent to finding the very first carnivores or vertebrates!

WHY SHOULD WE STUDY BRINE MICROBES?
There are more microbes in our oceans than stars in the universe [ ]! Yet, more than % of the total microbial diversity remains unexplored. The discovery of new microbes and the study of their abilities are always exciting. We keep uncovering new ways that microbes impact our planet and all life on Earth.
Because microbes can grow in such unique conditions, those from extreme environments are often a source of valuable new molecules.

EXTREME ENVIRONMENT
Place with conditions that are very di erent from the ones that we are able to live in. Some examples include high or low temperatures, acidic or alkaline conditions, high pressure, or high salinity.
Their range of applications is so wide that these molecules are seen as the future solutions on how to feed, fuel, and heal the world [ ]. Microbes from the brines of the Red Sea also seem to be very useful. Some show anti-cancer activity, while others seem capable of producing bioplastics (biologically-produced plastics that do not rely on the use of oil), cleaning up oil spills, or even capturing carbon dioxide [ ]. Scientists think that some of these microbes could be used to restore contaminated sites or even to prevent climate change! Studying extreme environments like the deep-sea brines also helps kids.frontiersin.org October | Volume | Article | Antunes Red Sea to Red Planet

Figure Figure
The have been picked as priority targets for astrobiological studies. Several of these microbes are being tested in simulation chambers and in balloon trips to the upper layers of earth's atmosphere. A selected few will even be sent to the International Space Station for space-exposure experiments. These studies will allow us to see if these microbes can survive and grow when exposed to space or to conditions found on Mars.

CONCLUSION
The deep-sea brines of the Red Sea are amazing, extreme environments unlike any other on our planet. These brines are important for many di erent fields. They are a source of exotic new microbes, new applications, and are also useful in the search for extraterrestrial life. We have only just started to explore deep-sea brines and their inhabitants and can expect many new findings in the near future. . Deep hypersaline anoxic basins as untapped reservoir of polyextremophilic prokaryotes of biotechnological interest. Mar. Drugs : . doi: . /md . Antunes, A., Olsson-Francis, K., and McGenity, T. J.

REFERENCES
. Exploring deep-sea brines as potential terrestrial analogues of oceans in the icy moons of the outer solar system. Curr. Issues Mol. Biol. : . doi: . /cimb. .

CONFLICT OF INTEREST:
The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
COPYRIGHT © Antunes. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

CHLOE, AGE:
Hello! My name is Chloe, I am currently years old. My hobbies include reading, singing, writing, and researching. I love to spend hours reading online or with paperback, depending on my mood, I just love to read. I am currently living with my two Persian cats that love to sing in the night like me and are both lazy like me. In the future, I would like to be a virologist or a genetic scientist, if I do not get to be one of them, I am just gonna be an author…

FABIÁN, AGE:
Fabián is a world traveling, years old, seventh grade polyglot who loves the ocean and being creative. His hobbies are: mountain biking, lego, inventing, acting, and reading, but especially reading. He loves being a part of the Frontiers for Young Minds program and looks forward to next year!

XENIA, AGE:
My name is Xenia. I like Science and I think it is awesome to be able to read a scientific article and actually understand what it says. In my spare time I like to read, do gymnastics, and take pictures.

ANDRÉ ANTUNES
I am an Associate Professor and leader of the Astrobiology Unit of the State Key Laboratory of Lunar and Planetary Science at the Macau University of Science and (Macau, China). I study life on the edge and exotic new microbes living in unexplored extreme environments, from salty lakes, to mines, to deep-sea locations. Many of these environments have conditions similar to those found on Mars and other planets. Studying these environments helps us when looking for life outside our planet and allows us to find the limits of life. Extreme environments are a source of unusual new species and new applications that can help us to feed, fuel, and heal the world. *aglantunes@must.edu.mo