Something extraordinary has happened in the world of space science, and it could change how we think about the origins of life. Scientists analysing samples from asteroid Bennu have discovered all five nucleobases found in DNA and RNA—the fundamental building blocks of life. This discovery means that essential components for life didn’t just form on Earth; maybe they arrived from space, delivered by asteroids billions of years ago.
For us, this is a thrilling opportunity to connect the studies of space, chemistry, and biology and to explore one of the biggest scientific questions: Where did life come from?
What is Asteroid Bennu?
Bennu is a 4.5 billion-year-old asteroid. It’s currently about 59 million kilometres away. As a comparison, this is roughly equal to the closest distance from Earth to Mars (which in 2003, when Mars was the closest in our modern lives, was about 55.7 million kilometres), but it can come as close as 299,000 km, roughly less than the distance from Earth to the Moon. The average distance from Earth to the Moon is 384,000 km and the closest distance to the Moon is 363,000 km. If only this were the most interesting thing!
Bennu was not the first asteroid to be sampled. The first asteroid to be sampled was Itokawa in 2010, followed by Ryugu, both by the Japanese Space Agency JAXA. Bennu, however, was the first asteroid mission to have a rock star part of the team – Queen’s guitarist Brian May. Brian May helped NASA return the sample by imagining a very clever way of creating stereoscopic images from the spacecraft’s data. This allowed the mission leader, Dante Lauretta, and the team to locate a safe site to land and collect a sample.
Sir Brian May and Professor Dante Lauretta with their book that tells all about their work and the asteroid.
What was found on asteroid Bennu?
NASA’s OSIRIS-REx mission collected samples from Bennu, a carbon-rich asteroid that formed in the early Solar System. When scientists analysed these samples, they found something incredible:
- All five nucleobases – adenine, guanine, cytosine, thymine (found in DNA), and uracil (found in RNA).
- Organic compounds, including carbon, nitrogen, and ammonia – essential ingredients for life.
- Salts and water-altered minerals, indicating that liquid water once interacted with the asteroid’s material.
These findings support the hypothesis that the fundamental components of life were already present in space and may have been delivered to early Earth via meteorite impacts.
Why is this a big deal?
The presence of nucleobases on an asteroid is a game-changer for astrobiology. It strengthens the idea that life’s essential chemistry may be widespread in the universe. There are five nucleobases, which fall into two categories:
1. Purines (larger, double-ring structures)
• Adenine (A)
• Guanine (G)
2. Pyrimidines (smaller, single-ring structures)
• Cytosine (C)
• Thymine (T) – found only in DNA
• Uracil (U) – found only in RNA, replacing thymine
These nucleobases form the “letters” of the genetic code. In DNA, they pair up to form the famous double helix structure:
• A pairs with T (or U in RNA)
• C pairs with G
What does it mean?
Brief Overview of Origin of Life Models
Scientists have proposed several models for how life might have originated on Earth. Some of the most prominent include:
1. The RNA World Hypothesis – Suggests that RNA was the first self-replicating molecule before DNA and proteins evolved. RNA can both store genetic information (like DNA) and catalyse chemical reactions (like proteins), making it a strong candidate for the earliest biomolecule.
2. The Metabolism-First Hypothesis – Proposes that simple chemical reactions in hydrothermal vents created energy cycles that later led to more complex molecules, eventually forming life.
3. The Panspermia Hypothesis – Suggests that life or its building blocks were delivered to Earth via asteroids, comets, or cosmic dust. The discovery of nucleobases on Bennu adds evidence to this idea.
4. The Hydrothermal Vent Model – Proposes that life began near deep-sea vents, where heat and chemical-rich water provided the right conditions for complex molecules to form.
5. The Lipid World Hypothesis—Supported by studies with hot springs, including in New Zealand, this hypothesis suggests that fatty molecules (lipids) formed the first protocells, creating compartments where life’s chemistry could take place.
How the Discovery of Uracil & Thymine Challenges the RNA World Hypothesis
The RNA World Hypothesis has been the leading theory for decades because RNA can store information and catalyze reactions. One of its key features is that early life only needed RNA, not DNA.
However, the discovery of both uracil (RNA’s nucleobase) and thymine (DNA’s nucleobase) on an asteroid challenges this view because:
• If RNA came first, why is thymine also present in space? This suggests that DNA-related chemistry was already happening at the same time as RNA, instead of evolving later.
• This could mean that RNA and DNA co-existed from the start, rather than RNA evolving first and then DNA appearing later.
• It raises the possibility that life’s origins involved a mix of nucleic acids, not a single RNA-dominated stage.
This discovery does not disprove the RNA world but expands the conversation about how life might have started. It suggests that DNA precursors may have been present much earlier than previously thought, hinting at a more complex prebiotic chemistry than the traditional RNA-first model.
💡 Key Idea for Students: If the building blocks of life exist beyond Earth, could life itself be common?
The discovery also connects with the long-standing panspermia hypothesis, which suggests that life or its ingredients could travel across space on asteroids or comets, seeding planets like Earth. This opens up fascinating discussions for the classroom about how life might emerge elsewhere in the universe.
Scientists have expressed profound interest in these findings, as they bolster the hypothesis that life’s building blocks may have been delivered to Earth via celestial bodies like asteroids and meteorites. For instance, the detection of uracil in samples from the asteroid Ryugu suggests that such prebiotic molecules were formed in space and could have contributed to the emergence of life on Earth. (Reuters, Sciencemediacentre.es)
How This Connects to the New Zealand Science Curriculum
For us, this discovery provides a fantastic cross-disciplinary learning opportunity. It connects to multiple strands of the curriculum:
🔬 Biology: Understanding nucleic acids (DNA/RNA) and the chemical basis of life.
🪐 Earth & Space Science: How asteroids and meteorites influence planetary evolution.
🧪 Chemistry: Organic molecules, prebiotic chemistry, and the conditions necessary for life.
📡 Technology & Science Communication: The role of space missions like OSIRIS-REx in advancing human knowledge.
Discussion Questions for the Classroom
- What does the discovery of DNA and RNA nucleobases on an asteroid suggest about the origins of life on Earth?
- If asteroids can carry the ingredients for life, what does this mean for the possibility of life on other planets?
- How do missions like OSIRIS-REx help us understand our own planet’s history?
- Could life exist in forms different from DNA-based organisms? How might we detect them?
- 🎸 If a rock star like Brian May can help uncover the secrets of space rocks, comment on how asteroids might be the real stars of the origins of life.
Taking It Further: Hands-On Activities
🚀 Modeling DNA & RNA – Use classroom kits or 3D models to help students visualize nucleobase structures.
🪨 Meteorite Chemistry – Investigate local or historical meteorite falls in New Zealand and their potential contribution to scientific research. The most recent meteorite found was through the efforts of Fireballs Aotearoa https://fireballs.nz https://youtu.be/d55iI1_YF7M
📷 Get involved in the meteorite hunt! Acquire a Meteor Camera for your school. https://fireballs.nz/get-involved/
🌓 Astrobiology Debate – Students can debate whether life likely originated on Earth or was seeded from space.
📡 Follow the Science – Track the next steps of OSIRIS-REx and how scientists continue to analyze asteroid samples.
Conclusion: A New Chapter in Understanding Life’s Origins
This discovery is one of the most exciting in space science and astrobiology. It provides strong evidence that the raw materials for life are not unique to Earth but are instead part of the fabric of space. For students in New Zealand and worldwide, it’s an incredible reminder that science is an ever-evolving field, full of mystery and discovery.
As we continue to explore asteroids, exoplanets, and the possibility of life elsewhere, we are reminded of how interconnected the universe truly is. This is an extraordinary discovery that was possible through the hard work of teams of curious people. Who knows? The next big discovery might come from a student inspired by these findings today.
More links
🔗 NASA OSIRIS-REx Mission
🔗 Nature Article on the Bennu Findings
🔗 Uracil in the carbonaceous asteroid (162173) Ryugu
🔗 Organic matter and water from asteroid Itokawa
Keep looking up!
