Dalia Kirshenblat is a proud graduate of Ithaca College’s class of 2020 with a degree in Science Writing and Communication. Dalia has extensive experience working with museums like the American Museum of Natural History in New York and the Ithaca Sciencenter. Dalia also works with science outreach organisations like Cornell University’s Spacecraft Planetary Imaging Facility (SPIF) and the Alex Hayes research group COMPASSE: Comparative Planetology & Solar System Exploration. Dalia is currently writing an astrobiology book for children and young adults.
Life began the moment that information molecules started to reproduce and evolve via natural selection. But how did this actually happen? While we don’t have a time machine, we can look to other worlds in the solar system and beyond to uncover the secrets of life’s beginnings. Consequently, the closer we look at the origins of life, the broader our search for life in space becomes.
We mainly look for life in the universe by looking for biosignatures, or clear signs of past or present life, ideally in the form that a simple experiment could identify. By studying what chemical traces organisms leave behind on Earth, we know what chemical clues to look for on other worlds. Trees, plants, and plankton in the ocean faithfully replenish oxygen in our atmosphere. This leads us to look for high levels of oxygen in the atmospheres of exoplanets, or planets orbiting other stars. We tend to think of the search for life as linear in this way: by studying life on Earth we develop better tools to look for life in space. But astrobiology is really more of a cycle.
If we do find extraterrestrial life, even in microbial form, we may very well uncover secrets about the prebiotic history of our own biodiversity. In other words, there is a cyclical nature intrinsic to the search for life: Earth life gives us the secrets to finding life in space, only to hope that life in space will one day reveal hidden secrets about life on Earth.
We are closer to finding life in the cosmos than ever before. Over the coming decades, a helicopter-like drone will glide through the skies of Saturn’s moon Titan, soaring over methane lakes and electrified sand-dunes. An orbiter will survey the surface of Jupiter’s moon Europa, searching for subsurface seas and byproducts of metabolism. New rovers will land on Mars, and we’ve already tasted the plumes of Saturn’s moon Enceladus, sampling its eruptive, icy ocean.
No one knows how life began on Earth, billions of years ago. We do, however, have some ideas about where it started, which gives us clues on where to look for life elsewhere. Early Earth had the chemical ingredients for life, but chemicals can’t do anything without outside energy. One of the leading theories on where life began on Earth is around hydrothermal vents: cracks in the Earth at the bottom of the ocean that spew out hot chemical-laden fluids, possibly giving rise to the first cell membranes. Through studying solar system moons like Enceldaus and Europa, and the anticipated hydrothermal vent environments deep within their dark, icy seas, we might concretely identify that life first arose in the deep sea on Earth. Or from studying Saturn’s moon Titan, a moon whose chemistry is eerily reminiscent of early Earth, we could discover how life arose from non-living matter billions of years ago.
But how do we look for life if we don’t know what we’re looking for? As we investigate life’s origins, we expand the scope of what we look for in the search for extraterrestrial life. The cycle continues.
On a mission to uncover the chemical origins of life, a team of researchers led by Dr. Steven Benner, founder of the Foundation for Applied Molecular Evolution in Alachua, Florida, came up with innovative methods to search for alien life by way of synthetic DNA. The Benner group spent decades studying the chemical conditions needed to produce self-replicating RNA (thought to be the precursor of life on Earth) from a prebiotic soup of molecules stirring in an early Earth Crock-Pot. From this, Benner’s team created a synthetic, eight-letter genetic language that seems to store and transcribe information just like the natural, four-chemical DNA that is the basis for all life on Earth, suggesting that there is nothing particularly magical about the four chemicals that evolved on Earth billions of years ago.
Like lego pieces clicking perfectly into microscopic holes and prongs, Benner’s team created new synthetic bases which combine with DNA’s natural nucleobases (A, T, C and G). The synthetic DNA, named Hachimoji, can be predictably transcribed into RNA, which is essential for life. RNA takes the information stored in DNA and gives it to proteins, and in terms of living beings, proteins do everything.
So how does this study of Earth life translate into the search for alien life? One way we might try to look for alien life is by creating something “alien” on Earth. If life on other worlds isn’t carbon-based, or doesn’t use our DNA, how could we recognize it? Using synthetic biology to make life-detecting instruments is a start. Regardless of chemical composition, no matter how foreign or extreme, if the structure of alien life (microbial or otherwise) resembles the structure of DNA, we should be able to detect it.
As a result of Dr. Benner’s research on synthetic DNA, and therefore the investigation into the precursors of life on Earth, we are closer than ever to detecting life that is chemically completely different to our own. One can only imagine what discovering life elsewhere will illuminate in our own biological history, and reveal for the future of life on Earth.