Scientists create precursor to life in thermal vent experiment
Scientists speculate that if life were to have spontaneously developed on Earth, the first thing there would need to be are vesicles.
- The findings also suggest that life may have formed in the deep oceans of other celestial bodies in our solar system as well.
- These are a lot like cell membranes, only they don't contain any of the complicated machinery that real, living cells do.
- Researchers recently demonstrated that these vesicles form frequently in environments similar to the hydrothermal vents of early Earth.
One of the hallmarks of life is homeostasis, or the ability for life to maintain a consistent internal state regardless of external conditions. Think of how you sweat to cool down, or how you need to drink water every now and again to maintain fluid levels.
This need to maintain homeostasis is present in all forms of life by definition. But in order for there to be homeostasis, there needs to be an inside and an outside. Now, a new study published in Nature Ecology & Evolution on November 4, may have identified how life first developed the barriers between cells' insides and their outsides.
What are vesicles?
Examples of a lipid bilayer, a liposome (a.k.a., a vesicle, or a protocell), and a micelle, which is a type of structure composed of only one layer of lipids.
Image source: Wikimedia Commons
Biologists believe that before life could develop on Earth, the first thing that needed to occur was the development of protocells. You can think of this like a cell minus all of the machinery that makes a cell work. Instead, a protocell is just composed of a membrane that defines inside and outside.
Nearly every organism's cell membrane is composed of a lipid bilayer, meaning that it's likely that life started out with these bilayers. A lipid is what's known as an amphiphilic molecules, which are molecules that have one side attracted to water and one side repelled by it. When there are two "sheets" of these molecules, they can form a barrier where the water-loving heads of the molecules face outward while the water-hating tails face inward. Sometimes, these sheets also form a sphere, or vesicle. These vesicles are essentially cell membranes.
Many scientists believe that the formation of vesicles was the first step toward life. Vesicles keep certain material out of the protocell while protecting an internal solution — homeostasis. But the question of where and how they formed is less clear.
Could vesicles have formed around hydrothermal vents?
An artists depiction of the water vapor plumes found on Enceladus, which are believed to caused by subsurface hydrothermal vents.
Image source: NASA / JPL-Caltech
The earliest direct evidence of life dates back to 3.5 billion years ago in the form of fossilized microorganisms, but life clearly existed before then. A 2017 study claims to have identified fossilized microorganisms dating back to 4.28 billion years ago, a mere 400 million years after the formation of the Earth itself. But this finding is contested, not just because it implies life sprang into action as soon as it could but because of where it was found: in the precipitate of hydrothermal vents.
The interesting chemistry and energy source that characterized hydrothermal vents has long made them a candidate for the origin of life, but experiments have failed to demonstrate that vesicles can form there. The environment around hydrothermal vents in the Hadean/early Archaean period when life began was highly alkaline, or basic, and extremely salty, even saltier than today's oceans are. When scientists attempted to create vesicles under such conditions, they simply fell apart, leading some scientists to argue that life probably began in freshwater pools, away from the highly alkaline and salty environment of hydrothermal vents.
However, this new study indicates that not only can protocells develop in this environment, it actually encourages their development. One of the study's authors, Dr. Sean Jordan, explains why their results were different: "Other experiments had all used a small number of molecule types, mostly with fatty acids of the same size, whereas in natural environments, you would expect to see a wider array of molecules."
Then and now.
Prior experiments were extremely precise, failing to replicate that messier nature of the hydrothermal vent environment — Jordan's experiment, however, featured numerous amphiphilic molecules. In fact, molecules with longer carbon chains required the heat of a hydrothermal vent to form vesicles, the alkalinity helped the vesicles keep their electrical charge, and the salt in the solution ensured helped the molecules pack together more tightly.
Not only does this suggest that life on Earth may have started in the deep oceans by hydrothermal vents, it also points to places in our solar system where life may develop or have developed as well. Celestial objects such as Europa, one of Jupiter's moons, may harbor life despite the miles-deep shell of ice that encases it. The moon's orbit constantly squeezes and unsqueezes it, providing heat for a liquid subsurface ocean that observations suggest may be salty and alkaline as well. Saturn's moon Enceladus is covered in geysers shooting water vapor, thought to be caused by hydrothermal vents, that contain salts and organic compounds.
Together, these facts paint a picture about the formation of life; not only might life first develop deep in the ocean near hydrothermal vents, but it might develop as soon as its able, and often. If this finding is backed up by further evidence, and if we find that life began nearly as soon as the oceans formed on Earth, we may have a very good shot at finding life in our solar system on the moons of Jupiter and Saturn.
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The idea of 'absolute time' is an illusion. Physics and subjective experience reveal why.
- Since Einstein posited his theory of general relativity, we've understood that gravity has the power to warp space and time.
- This "time dilation" effect occurs even at small levels.
- Outside of physics, we experience distortions in how we perceive time — sometimes to a startling extent.
Physics without time<p>In his book "The Order of Time," Italian theoretical physicist Carlo Rovelli suggests that our perception of time — our sense that time is forever flowing forward — could be a highly subjective projection. After all, when you look at reality on the smallest scale (using equations of quantum gravity, at least), time vanishes.</p><p style="margin-left: 20px;">"If I observe the microscopic state of things," writes Rovelli, "then the difference between past and future vanishes … in the elementary grammar of things, there is no distinction between 'cause' and 'effect.'"</p><p>So, why do we perceive time as flowing <em>forward</em>? Rovelli notes that, although time disappears on extremely small scales, we still obviously perceive events occur sequentially in reality. In other words, we observe entropy: Order changing into disorder; an egg cracking and getting scrambled.</p><p>Rovelli says key aspects of time are described by the second law of thermodynamics, which states that heat always passes from hot to cold. This is a one-way street. For example, an ice cube melts into a hot cup of tea, never the reverse. Rovelli suggests a similar phenomenon might explain why we're only able to perceive the past and not the future.</p><p style="margin-left: 20px;">"Any time the future is definitely distinguishable from the past, there is something like heat involved," Rovelli wrote for the <a href="https://www.ft.com/content/ce6ef7b8-429a-11e8-93cf-67ac3a6482fd" target="_blank"><em>Financial Times</em></a>. "Thermodynamics traces the direction of time to something called the 'low entropy of the past', a still mysterious phenomenon on which discussions rage."</p>
The strange subjectivity of time<p>Time moves differently atop a mountain than it does on a beach. But you don't need to travel any distance at all to experience strange distortions in your perception of time. In moments of life-or-death fear, for example, your brain would release large amounts of adrenaline, which would speed up your internal clock, causing you to perceive the outside world as moving slowly.<br></p><p>Another common distortion occurs when we focus our attention in particular ways.</p><p style="margin-left: 20px;">"If you're thinking about how time is <em>currently</em> passing by, the biggest factor influencing your time perception is attention," Aaron Sackett, associate professor of marketing at the University of St. Thomas, told <em><a href="https://gizmodo.com/why-does-time-slow-down-and-speed-up-1840133782" target="_blank">Gizmodo</a></em>.<em> "</em>The more attention you give to the passage of time, the slower it tends to go. As you become distracted from time's passing—perhaps by something interesting happening nearby, or a good daydreaming session—you're more likely to lose track of time, giving you the feeling that it's slipping by more quickly than before. "Time flies when you're having fun," they say, but really, it's more like "time flies when you're thinking about other things." That's why time will also often fly by when you're definitely <em>not</em> having fun—like when you're having a heated argument or are terrified about an upcoming presentation."</p><p>One of the most mysterious ways people experience time-perception distortions is through psychedelic drugs. In an interview with <a href="https://www.theguardian.com/books/2018/apr/14/carlo-rovelli-exploding-commonsense-notions-order-of-time-interview" target="_blank"><em>The Guardian</em></a>, Rovelli described a time he experimented with LSD.</p><p style="margin-left: 20px;">"It was an extraordinarily strong experience that touched me also intellectually," he said. "Among the strange phenomena was the sense of time stopping. Things were happening in my mind but the clock was not going ahead; the flow of time was not passing any more. It was a total subversion of the structure of reality."<br></p><p>It seems few scientists or philosophers believe time is completely an illusion.</p><p style="margin-left: 20px;">"What we call <em>time</em> is a rich, stratified concept; it has many layers," Rovelli told <em><a href="https://physicstoday.scitation.org/do/10.1063/PT.6.4.20190219a/full/" target="_blank">Physics Today</a>.</em> "Some of time's layers apply only at limited scales within limited domains. This does not make them illusions."</p>What <em>is</em> an illusion is the idea that time flows at an absolute rate. The river of time might be flowing forever forward, but it moves at different speeds, between people, and even within your own mind.
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