Cloud Chamber Physics: Brian Cox Explains Cosmic Mutations

In the history of Earth, cosmic rays may have played a larger role in evolution by flipping bits not in electronics but in the genetic codes of living organisms. These mutations provided some of the variation on which natural selection acts. This suggests that cosmic rays have been a constant factor in biological evolution, potentially contributing to genetic diversity over millions of years through random mutations caused by radiation exposure.

Cosmic rays may influence biological evolution by increasing mutation rates in living organisms. Since cosmic ray particles sometimes originate at the far reaches of the universe and can reach Earth's surface, they may occasionally penetrate deep enough to affect DNA within organisms. This raises the possibility that cosmic radiation has played a role in shaping evolutionary paths of species throughout Earth's history.

Although we are not consciously aware of it in our daily lives, this quantum rain of secondary particles is bombarding us constantly at this very moment. If you extend the palm of your hand toward the sky, several muons created by impacts of distant cosmic protons are passing through it right now, crossing your cells and subtly altering the molecular environment before burying themselves deeply in Earth's rocky crust. This natural ionizing radiation background has been one of the invisible engines of biological evolution throughout the history of life, inducing occasional genetic mutations in the DNA of living organisms.

Mutations in DNA that are seen on Earth are sometimes caused by cosmic rays. Supernova and other occurrences that occur in space are the sources of cosmic rays, which are particles that possess a great deal of energy. When they collide with the atmosphere of the Earth, they generate showers of secondary particles that make their way to the surface. On occasion, these particles can infiltrate living creatures, which can lead to DNA alterations. The majority of mutations are either innocuous or are fixed, however, there are a few that play a part in the evolution and genetic variety of species. The biological history of Earth is connected to the cosmos at large by the continuous reign of cosmic rays.

The radiation from supernovae causes mutations by breaking DNA bonds. While most mutations are harmful, occasionally they are beneficial. This steady source of cosmic radiation provided the right pace of genetic mutations throughout Earth's history - not too much to kill off all life, but not too little to prevent beneficial mutations. This radiation was essential for the evolution of new species. We are literally 'star stuff' - the carbon in our hands and oxygen in our lungs were forged in stars, while the iron in our blood came from stellar deaths. We are chemically and genetically tied to the universe.

Beyond Earth's magnetosphere, radiation becomes a major hazard. On Earth, annual radiation exposure is about 3 millisieverts, equivalent to about three chest X-rays, allowing the body time to recover. On the moon, dosage increases 200 times. Solar particles and cosmic radiation damage DNA, causing acute symptoms like fever, nausea, and vomiting, plus long-term problems like cancer and sterility. Most space agencies put a lifelong radiation cap around 1,000 millisieverts, permanently grounding astronauts who exceed it.

Spacecraft can be protected against radiation using materials like aluminum and plastic (specifically PET plastic), which contains hydrogen that blocks space radiation. Another strategy involves using astronaut waste as radiation shielding by attaching it to the exterior of the spacecraft. This approach is already used on the International Space Station. Emerging technologies like boron nitride nanotubes (BNNTs) are being developed as flexible radiation shields that can also be used to construct buildings on Mars after arrival.

NASA protects astronauts from space radiation through predictive modeling of solar activity and strategic shielding; solar eruptions produce harmful solar energetic particles (SEPs) that can damage DNA and increase cancer risk, while galactic cosmic rays provide constant low-level radiation throughout space travel, making accurate forecasting and multi-layered protection systems essential for safe lunar and Mars missions.

Different types of radiation require different shielding strategies. Lead is excellent for blocking X-rays and gamma rays on Earth, but in space, high-energy cosmic particles hitting heavy metals like lead can create secondary radiation, making the problem worse. Spacecraft are largely built from lightweight materials like aluminum, with water, fuel, and equipment positioned to provide additional shielding where most useful. The goal is reducing exposure to acceptable levels, not eliminating it entirely.

Using SpaceX's Starship specifications (50m tall, 9m diameter, 100-ton payload), calculations demonstrate that a 50cm thick water shield surrounding the crew compartment would require 239 tons of water—exceeding the ship's total payload capacity and providing minimal radiation protection, as studies indicate 2 meters of water is needed to reduce galactic cosmic ray exposure by half.

The heliosphere acts as a protective shield against cosmic rays - high-energy particles from supernovae that can damage DNA and disrupt electronics. Without this protection, cosmic ray bombardment at Earth's surface would be significantly higher. Studies suggest mass extinctions may correlate with periods when the heliosphere was compressed by dense interstellar clouds. Every star with a stellar wind creates an astrosphere protecting its planetary system, with sizes varying based on stellar mass, age, and local conditions. For planets to be truly habitable, they may need to exist within sufficiently protective astrospheres - too small an astrosphere exposes planets to harmful cosmic rays, while too unstable an astrosphere creates fluctuating radiation environments.

This section examines cosmic ray impacts on exoplanet atmospheres. Cosmic rays penetrate atmospheres and break N2 molecules into nitrogen atoms, which rapidly form NO. Increased cosmic ray flux (from active or flaring M dwarfs) dramatically increases NO production—up to 10,000× Earth levels. High NO levels destroy ozone through catalytic cycles, potentially eliminating the ozone biomarker even when life is present. Planetary protection from cosmic rays depends on magnetospheric shielding. Tidally locked planets face additional challenges: whether atmospheres can redistribute heat from hot day sides to cold night sides determines habitability. 3D modeling studies suggest most atmospheres can transfer sufficient heat, though cosmic ray exposure on the night side remains a concern for potential life.

Earth's magnetosphere protects the planet from harmful cosmic radiation by deflecting charged particles from the sun. This protective shield is essential for maintaining Earth's habitability and preventing damage to living organisms. The magnetosphere extends into space and works in conjunction with the atmosphere to provide comprehensive protection. This dual protection system is crucial for maintaining Earth's environmental conditions and supporting life.

All stars emit supersonic plasma winds carrying magnetic fields into interplanetary space. The magnetopause forms where Earth's magnetic pressure balances solar wind dynamic pressure, stopping stellar plasma from entering. This boundary lies 5-8 Earth radii out, far beyond our 60-km atmosphere, providing crucial protection. Without magnetospheres, atmospheres erode directly by stellar winds. Mars lost its global magnetosphere ~1.5 billion years ago and subsequently lost its atmosphere, now having only a 50-meter CO2 layer. This demonstrates that planetary magnetospheres are essential for atmospheric retention over geological timescales.

A magnetosphere is a protective magnetic field generated by a planet's rotation and liquid metallic core. Earth's magnetosphere protects the planet from cosmic radiation and solar wind by deflecting charged particles. Without this protection, cosmic radiation could damage DNA and cause genetic mutations, while solar wind could strip away the atmosphere. A strong magnetosphere is therefore essential for protecting life on a planet.