theSIGNAL SCIENCE
4 November 2026
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Science

All Five Letters of Life Found on an Asteroid

Japanese scientists have found every one of life's five genetic "letters" in dust from asteroid Ryugu, hinting that life's ingredients were everywhere.

Imagine opening a tiny capsule from deep space and finding the full alphabet of genetics inside. That is roughly what happened in a Japanese laboratory. The capsule held 5.4 grams of black dust from the asteroid Ryugu, brought home in 2020 by JAXA's Hayabusa2 mission.

Now a team of Japanese scientists reports, in Nature Astronomy, that the dust contains all five nucleobases. Why does that matter? Nucleobases are the "letters" of DNA and RNA: adenine, guanine, cytosine, thymine and uracil. Without them, no organism could grow, reproduce or evolve.

In 2023, an international team had found only one of them, uracil, in the Ryugu samples. Now the full set has turned up. The researchers worked under ultra-clean conditions, extracted the molecules with water and hydrochloric acid, and purified them for detection. Both samples they analysed contained all five, in roughly similar amounts.

Could this simply be contamination?

Photo: Viktor Talashuk / Unsplash
Black dust from asteroid Ryugu, returned to Earth in 2020, now reveals all five genetic nucleobases.
Discuss
  • Why do scientists worry about contamination in meteorites, and how do sealed asteroid samples solve that problem?
  • Finding the same molecules on Ryugu and Bennu suggests what about the early Solar System's chemistry?
  • Nucleobases are only the letters of life; what else might be needed to turn chemistry into biology?
Science

One Shot to Fix Cholesterol Forever?

Picture swallowing no pills for decades, yet your cholesterol stays low. One injection might do it. Gene therapies already help children with spinal muscular atrophy and patients with sickle cell disease, and researchers now eye common problems like heart disease. But a one-time edit is permanent. Cardiologists Eric Smith and Venkatesh Murthy ask in JAMA Internal Medicine: if we can rewrite genetic activity, must we?…
  • Would you accept a permanent genetic change to avoid taking daily medication for life?
∞
Asteroids such as Ryugu and Bennu are remnants of the early Solar System that preserve materials from its youth.
Study team summary, Nature Astronomy report on Ryugu samples
Science

Hera Finally Sees Two Asteroids, Not One

One pixel. That is all Dimorphos amounts to in Hera's newest picture, yet it matters enormously. Until October 18, the European probe saw the Didymos system as a single dot of light; now, from 1,280 kilometers away, the little moonlet stands apart. It is pyramid-sized, circling its 780-metre parent at a gentle 18 centimeters per second. NASA knocked it off course in 2022.…
  • If humans can nudge an asteroid's orbit, who should decide when, and whether, to do it?
GLOBAL · Science
A simple blood test could reveal Alzheimer’s risk 10 years before symptoms
AFRICA · Science
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AMERICAS · Science
Common pesticide linked to 2.5 times the risk of Parkinson’s disease
WORLD · Science
A hidden star is plowing through Betelgeuse’s atmosphere, new evidence suggests
theSIGNAL IN THE LAB
1VOCABULARY
nucleobasescontamination
pristinehauntedmoonlet
permanentscattered
2GRAMMAR FOCUS
Inversion with negative adverbials (Not only did..., Hardly had..., Never have..., No sooner had... than...)
When a negative or restrictive adverbial (e.g. not only, hardly, no sooner, rarely, never, only then) opens a sentence, the auxiliary verb comes before the subject, as in a question: 'Not only did the team find uracil...' The structures 'Hardly/Scarcely had... when' and 'No sooner had...…
did · had · than · when · have · Only · Little
  1. Not only the scientists find uracil in the Ryugu dust, but they also detected the other four nucleobases.
  2. Hardly the capsule been opened when researchers began analysing the black dust.
  3. No sooner had the molecules been extracted with water and acid the team started purifying them for detection.
  4. Never meteorite researchers been able to rule out contamination completely, because such samples had spent time on Earth's surface.
  5. Scarcely had Hera spotted the tiny moonlet scientists began planning detailed measurements.
  6. Only after the Bennu samples also yielded all five nucleobases researchers gain a second, independent check.
3DEPENDENT PREPOSITIONS
Complete each phrase with the correct preposition. All from today’s articles.
  1. The researchers extracted the molecules ___ water and hydrochloric acid.
  2. A team of Japanese scientists reports ___ Nature Astronomy that the dust contains all five nucleobases.
  3. Doubts always lingered because the meteorites had spent time ___ Earth's surface.
  4. The samples were sealed ___ our biosphere to prevent contamination.
  5. Gene therapies already help patients ___ sickle cell disease.
4CRITICAL THINKING
Two of today's stories involve technology that changes the world in ways that cannot easily be reversed, whether it is rewriting human genes or altering an asteroid's path. Is it possible to weigh a long-term risk fairly when the benefits are immediate and the consequences may only appear generations later? Who should have a voice in such decisions, and who might be left out?
5CREATIVE · HEADLINES
Write a headline for the top story in each of the following styles. One line each, no explanation:
  • TABLOID NEWSPAPER
  • LUXURY MAGAZINE
  • ACTIVIST BLOG
6WRITING
Imagine you are a scientist who has just opened a capsule of asteroid dust, a gene-editing clinic is advertising a one-off cholesterol cure, and a probe has spotted a tiny moonlet. Write a short diary entry (80-100 words) describing which of these three discoveries you find most exciting, and which one worries you most.
7DEGREES OF EXTREMITY
Complete each ladder from mild to strong.
  • The discovery was quite surprising.→→
  • Scientists were rather doubtful about the results.→→
  • The samples were fairly clean.→→
  • The finding is quite important for researchers.→→
  • The gene therapy is somewhat controversial.→→
  • Dimorphos is pretty small.→→
8SPEAKING
  1. Which would amaze you more: finding microbes on Mars or on Europa?
  2. How would you explain this discovery to a ten-year-old in one minute?
  3. Which space mission from the past decade has impressed you most, and why?
  4. Do you think curiosity or practical benefit should drive space exploration funding?