The search for alien life is far too human-centric. Our flawed understanding of what life really is may be holding us back from important discoveries about the universe and ourselves.
- What, should it exist, is the universal law that connects all living things? To even dream of answering that question, and to one day find alien life elsewhere in the cosmos, humans must first reconcile the fact that our definition of life is inadequate.
- For astrobiologist Sara Walker, understanding the universe, its origin, and our place in it starts with a deep investigation into the chemistry of life. She argues that it is time to change our chemical perspective—detecting oxygen in an exoplanet's atmosphere is no longer sufficient enough evidence to suggest the presence of living organisms.
- "Because we don't know what life is, we don't know where to look for it," Walker says, adding that an unclear or too narrow focus could result in missed discoveries. Gaining new insights into what life on Earth is could shift our quest to find alien life in the universe.
The study identified superhabitable planets outside of our solar system.
- The odds are that if Earth had the right conditions for the development of life, other places probably do, too.
- Scientists have identified two dozen planets that match some items on the list of desirable traits.
- All of these planets are too far away to reach with current tech, but may be valuable research targets.
Superhabitable<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDQ3MzYwNC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYxMjYwOTE5NX0.7WH5907n-K3Ew9QP96D1ohm_yUDEcwH_XjnDwnICYQM/img.jpg?width=980" id="206f9" class="rm-shortcode" data-rm-shortcode-id="ef375f57087011a2324d7f086e3b96c1" data-rm-shortcode-name="rebelmouse-image" data-width="5350" data-height="3667" />
The 24 candidates in their habitable zone near K dwarf stars
Credit: Schulze-Makuch, et al./Astrobiology<p>On the other hand, all that desirable real estate is pretty far away — none of these 24 "superhabitable" planets are less than 100 light years from Earth. They were identified in a study led by geologist <a href="https://news.wsu.edu/tag/dirk-schulze-makuch/" target="_blank" rel="noopener noreferrer">Dirk Schulze-Makuch</a> of WSU and Technical University in Berlin, Germany. He was joined in the research by astrophysicists <a href="https://www2.mps.mpg.de/homes/heller/" target="_blank">René Heller</a> of the Max Planck Institute for Solar System Research in Germany and <a href="https://email@example.com&xsl=bio_long" target="_blank">Edward Guinan</a> of Villanova University.</p><p>The open-access study is published in the journal <a href="https://www.liebertpub.com/doi/10.1089/ast.2019.2161" target="_blank">Astrobiology</a>.</p><p>Ignoring the possibility that other planets might be even more likely to support life than ours is, after all, like someone insisting they live in the best country in the world without having visited any others. The study puts it this way: "Neglecting this possible class of 'superhabitable' planets, however, could be considered anthropocentric and geocentric biases."</p><p>In searching for superhabitable planets among the 4,500 known candidates, the scientists were not so much looking for somewhere for us to escape to as they were spotting planets that were most likely to be populated by intelligent life. Their hope is to offer up interesting targets for future investigation by instruments such as the European Space Agency's <a href="https://sci.esa.int/web/plato" target="_blank" rel="noopener noreferrer">PLATO space telescope</a>, as well as NASA's <a href="https://www.jwst.nasa.gov" target="_blank">James Webb Space Telescope</a> and <a href="https://asd.gsfc.nasa.gov/luvoir/" target="_blank" rel="noopener noreferrer">LUVOIR space observatory</a>.</p><p>Schulze-Makuch tells <a href="https://news.wsu.edu/2020/10/05/planets-may-better-life-earth/" target="_blank">WSU Insider</a>:</p><p style="margin-left: 20px;">"With the next space telescopes coming up, we will get more information, so it is important to select some targets. We have to focus on certain planets that have the most promising conditions for complex life. However, we have to be careful to not get stuck looking for a second Earth because there could be planets that might be more suitable for life than ours."</p><p>Before one can go searching for superhabitable planets, once must figure out what that word means.</p>
Blame it on the sun<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDQ3MzYxNC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY2NjAwNDUyNn0.bv9FioVLoHPE7IxjWnmRzfNKkeGI6UOioEorxSqMapU/img.jpg?width=980" id="7f28c" class="rm-shortcode" data-rm-shortcode-id="5613866aa3c976f165e51f4565517e90" data-rm-shortcode-name="rebelmouse-image" data-width="1440" data-height="681" />
Credit: Tungdil Preston/Unsplash<p>The scientists first had to work out the type of sun a superhabitable planet would be most likely to orbit. Interestingly, they decided against dwarf type G stars — also known as "dG stars" — similar to our own sun. After all, they write, "Since it took about 3.5 billion years on Earth until complex macroscopic life appeared, and about 4 billion years for technologically advanced life (us), life on many planets orbiting dG stars may simply run out of time."</p><p>Another issue is that young dG stars spin 10 times as fast as our mature Sun now does, producing "high levels of magnetic dynamo-driven activity and very intense coronal X-ray and chromospheric FUV emissions, which makes the origin and early evolution of life challenging."</p><p>The study settles on planets orbiting type K stars. These stars are a bit cooler than ours and less luminous, but they live a long time, longer than the Sun, from 20 to 70 billion years. This would give their planets more time to get life going.</p>
Size matters<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDQ3MzYxNy9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYxNjkxMzg4Nn0.x8YqDvGmdmooMUSRu7oJCGTKiwg5VPrqZaoboVOa5fQ/img.jpg?width=980" id="f48b4" class="rm-shortcode" data-rm-shortcode-id="372b444990b8ca7a2520d3bca8124851" data-rm-shortcode-name="rebelmouse-image" data-width="1440" data-height="810" />
Credit: AleksandrMorrisovich/Shutterstock<p>Planets with a greater mass than ours were deemed desirable for a few reasons, so long as they were not so big as to become gas giants and so on. These planets would have robust, thick atmospheres, slightly higher temperatures for nurturing life, and lots of elbow room: "This would have advantages for the distribution of species and settlements of islands and continents."</p>
Environmental requirements<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDQ3MzYyNC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY1MjQ4NzM5Mn0.9dDvWvYfJY63wX2QbZ0SnITCtsSAMzAoK0H4pfG7D8Q/img.jpg?width=980" id="d973e" class="rm-shortcode" data-rm-shortcode-id="b2e925bc9949378ce37bbc318ff35493" data-rm-shortcode-name="rebelmouse-image" data-width="1440" data-height="810" />
Credit: BeeBright/Shutterstock<p>The researchers also settled on an environmental checklist for superhabitable planets. Based on the conditions that allowed life to form on Earth, a planet would have to have the following life-supporting conditions as explained in the study:</p><ul><li><em>T</em><em>emperatures</em> —"Submarine hydrothermal systems, geothermal hot springs, brine pockets in sea ice at about −30°C, deep continental areas"</li><li><em>pH</em> — "Acid mine drainage, geothermal sulfurous sites (e.g., Yellowstone) Soda lakes, peridotite-hosted hydrothermal systems (e.g., Lost City vent)"</li><li><em>Water activity</em> — "Deep-sea brines, soda lakes, evaporate ponds, dry soils and rocks, food with high solute content"</li><li><em>Lower O2 content </em>— "Anoxic marine or lacustrine sediments, intestinal organs, early Earth environments"</li><li><em>Pressure</em> — "Deep oceanic trenches such as the 11,100 m deep Marianas Trench, Martian surface conditions (based on laboratory experiments)"</li><li><em>Radiation</em> — "No natural source of radiation on Earth at levels tolerated by D. radiodurans"</li><li><em>Chemical extremes</em> — "Submarine hydrothermal vent fluids and sulfides; some high-metal containing lakes"</li></ul>
We have some winners. Sort of.<p>Of the superhabitable candidates the study detected, none totally meet the researchers' criteria, though one has four of them, meaning it may be more likely to have life on it than Earth did, and it might be a place we could consider quite comfy.</p><p>Concludes Schulze-Makuch, "It's sometimes difficult to convey this principle of superhabitable planets because we think we have the best planet. We have a great number of complex and diverse lifeforms, and many that can survive in extreme environments. It is good to have adaptable life, but that doesn't mean that we have the best of everything."</p>
Scientists have detected within the Venusian atmosphere a chemical known to be a byproduct of life.
- A team of researchers has detected significant amounts of phosphine within the cloud deck of Venus.
- Computer simulations suggest that the amount of phosphine in the Venusian atmosphere couldn't have been produced by known inorganic processes.
- The findings aren't conclusive evidence of alien life, but they do suggest Venus shouldn't be overlooked in the search for alien life.
Pioneer Venus orbiter illustration
NASA<p>It's not conclusive evidence of life: Phosphine (PH3) can be produced through inorganic processes, like interactions involving sunlight, surface minerals, volcanic activity, and lightning. </p><p>But the study authors considered these and other potential sources, and they created computer models to test whether they could simulate the production of phosphine on Venus. The results produced small amounts of the chemical, but not nearly as much as multiple observatories have detected within the cloud decks of Venus.</p><p>So, for now, scientists don't know what's producing the phosphine. Alien life remains a plausible explanation.</p><p style="margin-left: 20px;">"Technically, biomolecules have been found in Venus' atmosphere before, but these molecules are also associated with a thousand things other than life," study co-author Clara Sousa-Silva told <a href="https://news.mit.edu/2020/life-venus-phosphine-0914" target="_blank">MIT News</a>. "The reason phosphine is special is, without life it is very difficult to make phosphine on rocky planets. Earth has been the only terrestrial planet where we have found phosphine, because there is life here. Until now."</p>
The mission could launch as soon as the 2030s, the researchers said.
- A team of scientists have been developing a proposal that would send a semi-autonomous submarine to explore the seas of Titan, Saturn's largest moon.
- Titan is the only body in our solar system that has large bodies of liquid on its surface.
- It's also a top candidate in the search for alien life.
Why study Titan?<p>Titan has long been a top candidate for space research and the search for alien life within our solar system. But scientists didn't know much about the Mercury-sized moon until 2004, when NASA's Cassini spacecraft began conducting flybys of Titan, and later landed the <em>Huygens </em>probe on the moon's surface.<br></p><p>That mission revealed that Titan is actually more like Earth than our Moon: Titan has an atmosphere with organic molecules and complex chemistry. It has rain and <a href="http://spaceref.com/saturn/violent-methane-storms-on-titan-may-explain-dune-direction.html" target="_blank">storms</a>, which help to shape the dunes on its surface. And it has maria (seas) and lacus (lakes), some larger than the Great Lakes of North America. Besides Earth, no other body in our solar system has liquid on its surface like Titan does.</p>
Hollywood has created an idea of aliens that doesn't match the science.
- Ask someone what they think aliens look like and you'll probably get a description heavily informed by films and pop culture. The existence of life beyond our planet has yet to be confirmed, but there are clues as to the biology of extraterrestrials in science.
- "Don't give them claws," says biologist E.O. Wilson. "Claws are for carnivores and you've got to be an omnivore to be an E.T. There just isn't enough energy available in the next trophic level down to maintain big populations and stable populations that can evolve civilization."
- In this compilation, Wilson, theoretical physicist Michio Kaku, Bill Nye, and evolutionary biologist Jonathan B. Losos explain why aliens don't look like us and why Hollywood depictions are mostly inaccurate.