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Today, life on Earth is highly evolved, diverse, and complex.
This tree of life illustrates the evolution and development of the various organisms on Earth. Although we all emerged from a common ancestor more than 2 billion years ago, the diverse forms of life emerged from a chaotic process that would not be exactly repeated even if we rewound and re-ran the clock trillions of times. As first realized by Darwin, many hundreds of millions, if not billions, of years were required to explain the diversity of life forms on Earth.
Credit : Leonard Eisenberg/evogeneao
This complexity is relatively new, however, as earlier life was simpler.
This tunneling electron microscope image shows a few specimens of the cyanobacterium species Prochlorococcus marinus. Each one of these organisms is only about half a micron in size, but all together, cyanobacteria are largely responsible for the creation of Earth’s oxygen: both initially and largely even during the present day. Like all bacteria, their lifetime is much, much shorter than the lifetime of a human, and while cyanobacteria are relatively primitive organisms, they “only” date back to no earlier than 2.7 billion years ago, whereas life on Earth goes back more than a billion years, at least, farther than this.
Credit : Luke Thompson from Chisholm Lab and Nikki Watson from Whitehead, MIT
Foundational organic molecules — sugars, fats, and amino acids — serve as biological building blocks.
If life began with a random peptide that could metabolize nutrients/energy from its environment, replication could then ensue from peptide-nucleic acid coevolution. Here, DNA-peptide coevolution is illustrated, but it could work with RNA or even PNA as the nucleic acid instead. Asserting that a “divine spark” is needed for life to arise is a classic “God-of-the-gaps” argument, but asserting that we know exactly how life arose from non-life is also a fallacy. These conditions, including rocky planets with these molecules present on their surfaces, likely existed within the first 1-2 billion years of the Big Bang.
Credit : A. Chotera et al., Chemistry Europe, 2018
At some point, in Earth’s primitive environment, life first originated .
A planet that is a candidate for being inhabited will no doubt experience catastrophes, collisions, and extinction-level events on it, particularly during its early stages. If life is to survive and thrive on a world, it must possess the right intrinsic and environmental conditions to allow it to persist. Some scientists think these early impacts may have delivered water, amino acids, and other molecules useful to emerging life on Earth, as the evidence is strong that the impact and cratering rate across the Solar System was much higher than present for the first 0.6-0.7 billion years of our Solar System’s history.
Credit : NASA/Goddard Space Flight Center conceptual image lab
The biggest question of all — how life began — remains scientifically mysterious.
Early on, shortly after the Earth first formed, life likely arose in the waters of our planet. The evidence we have that all life that’s extant today can be traced back to a universal common ancestor is very strong, but many details concerning the early stages of our planet, for perhaps the first 1-to-1.5 billion years, remain largely obscure. While life arose early on, there is no evidence that Earth came into existence with life already on it, with the origin being uncertain to within 100-700 million years after our planet’s formation.
Credit : H. Betts et al., Nature Ecology & Evolution, 2018
We understand what early Earth’s primitive atmosphere was composed of.
The prospect of detecting and characterizing the atmosphere of a true Earth-like planet, i.e., an Earth-sized planet in the habitable zone of its star, including both red dwarf and more Sun-like stars, is within our reach. With a next-generation coronagraph, a large ultraviolet-optical-infrared mission could find dozens, or even hundreds, of Earth-sized worlds to measure.
Credit : National Academies/Astro2020 decadal survey
Beginning in the 1950s, experiments simulated that environment .
This photograph shows origin of life researcher Stanley Miller along with a series of flasks and glass tubing that allows for a performance of a version of the famed Miller-Urey experiments from the 1950s, where raw ingredients representing primitive Earth’s atmosphere are subject to energy injections and cold traps, resulting in the production of various complex organic molecules.
Credit : Roger Ressmeyer/Corbis; Science Magazine
With early Earth’s raw ingredients plus injected energy, complex molecules were formed .
This pictorial illustration shows the layout of the Miller-Urey experiment, where a large gas chamber containing a mix of primitive-Earth gases (water, methane, ammonia, hydrogen) is electrocuted, and cold water is pumped beneath it, allowing for condensation and the creation and trapping of complex molecules. That material is then recycled (right), heated, and pumped back into the gas mixture, enabling even more complex molecules to build up over time.
Credit : Carny/YassineMrabet/Wikimedia Commons
They included many varied amino acids, but also aldehydes: precursors to sugar.
The existence of complex, carbon-based molecules in star forming regions is interesting, but isn’t anthropically demanded. Here, glycolaldehydes, an example of a precursor molecule to sugars, are illustrated in a location corresponding to where they were detected in an interstellar gas cloud: offset from the region presently forming new stars the fastest. Interstellar molecules are common, with many of them being complex and long-chained.
Credit : ALMA (ESO/NAOJ/NRAO)/L. Calçada (ESO) & NASA/JPL-Caltech/WISE Team
In interstellar space, cyanides and carbon monoxide are common: also sugar precursors.
The chemical structures of the sugars Ribose and Glucose are diagrammed out, showcasing carbon bonds (dark gray), hydrogen atoms (small, white) and oxygen (red) as bonded in these molecules. These were the first two sugars discovered inside meteorites and on asteroids.
Credit : Cosmetic Ingredients Guide
And simple sugars — ribose and glucose — are found within meteorites .
This image shows a fragment of the Murchison Meteorite, which fell in Australia in 1969. The Murchison Meteorite is particularly rich in amino acids and other organic molecules, as analysis of the material inside has revealed approximately 80 amino acids so far, with left-handed and right-handed amino acids both represented abundantly. By comparison, only 22 amino acids participate in life processes on Earth, all of which are right-handed. With only one exception, all meteorite recovery operations have occurred over continents, not in the ocean waters.
Credit : Basilicofresco/Wikimedia Commons
Even in space, in situ , asteroids contain these sugars , too.
The asteroid Bennu, shown here, has a surface typical of most asteroids under ~1 km in diameter: it appears to be a volatile-rich pile of rubble. Analysis of material collected from Bennu shows the presence of in situ sugars, like ribose and glucose, indicating that these primitive relics from the Solar System’s formation can serve as a natural cosmic home and source of even complex organic molecules in great variety.
Credit : NASA’s Goddard Space Flight Center / Conceptual Image Lab / Scientific Visualization Studio
Interstellar gas clouds harbor many complex organic molecules.
This three-color composite shows the galactic center as imaged in three different wavelength bands by NASA’s Spitzer: the predecessor to the James Webb Space Telescope. Carbon-rich molecules, known as polycyclic aromatic hydrocarbons, show up in green, while stars and warm dust are also visible. A glow where our supermassive black hole sits is identifiable as well. The presence of ethyl formate was found in the gas cloud Sagittarius B2: the same molecule that gives raspberries their characteristic scent.
Credit : NASA/JPL-Caltech
Alcohols, polycyclic aromatic hydrocarbons, and fullerenes abound in space.
This infrared portrait of the Small Magellanic Cloud, located just 199,000 light-years away, highlights a variety of features, including new stars, cool gas, and quite spectacularly (in green) the presence of polycyclic aromatic hydrocarbons: the most complex organic molecules ever found in the natural environment of interstellar space. The way that atoms link up to form molecules, including organic molecules and biological processes, is only possible because of the Pauli exclusion rule that governs electrons, and happens everywhere across the Universe where enough heavy elements are present.
Credit : NASA/JPL-Caltech
Now, a new sugar has been found in space .
This image shows the magnetized galactic center, with various features highlighted, as imaged by the SOFIA/HAWC+ FIREPLACE survey team. The giant bubble at the left of the image is some 30 light-years wide, several times larger than any other supernova-blown bubble ever discovered. Located in this central molecular zone are several gas clouds, with one particular gas cloud near the center-left of the image representing the first detection of sugar in interstellar space.
Credit : D. Paré et al., arXiv:2401.05317v2, 2024
26,000 light-years away, near the galactic center, erythrulose abounds.
These 14 panels show radio data in a variety of (gigahertz) wavelengths that showcase the transitions of the molecule erythrulose, whose red bumps can be reconstructed as appearing in the data. The erythrulose signature is at least 8 times stronger than all evidence for any three-carbon sugar molecules: the first robust detection of a sugar molecule in interstellar space.
Credit : I. Jiménez-Serra et al., Nature Astronomy, 2026
This four-carbon sugar was spotted with multiple large radio telescopes.
The 30 meter IRAM radio telescope, shown here, is one of today’s largest and most sensitive single-dish telescopes for tracing the presence of millimeter waves of light. Along with the Yebes 40 meter telescope, a broadband spectral survey of the galactic center was conducted, yielding the first detection of sugar molecules in an interstellar gas cloud.
Credit : IRAM-gre/Wikimedia Commons
It’s the first sugar found in the interstellar medium : likely assembled atop dust grains.
This far-infrared view of the Taurus Molecular Cloud showcases cool dust grains that emit at only 10-30 K above absolute zero. According to astrochemistry models leveraging quantum chemistry calculations, the sugar erythrulose likely forms most efficiently atop interstellar dust grains, where two-carbon aldehydes and alcohols interact to lead to the production of a four-carbon sugar. This could be the origin of a sugar inventory: nutrients for early life to feed off of.
Credit : ESA/Herschel/NASA/JPL-Caltech; Acknowledgement: R. Hurt (JPL-Caltech)
These sugar reservoirs could provide nutrients for the first forms of life .
This aerial view of Grand Prismatic Spring in Yellowstone National Park is one of the most iconic hydrothermal features on land in the world. The colors are due to the various organisms living under these extreme conditions, and depend on the amount of sunlight that reaches the various parts of the springs. Hydrothermal fields like this are some of the best candidate locations for life to have first arisen on a young Earth, and may be home to abundant life on a variety of exoplanets.
Credit : Jim Peaco/National Parks Service
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This article Sugar in space: another step towards life’s origins is featured on Big Think .
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