University of California, Santa Barbaras professors Philip Lubin and Joel Rothman and their colleagues contemplate launching small cryptobiotic lifeforms into interstellar space.

Our ability to explore the cosmos by direct contact has been limited to a small number of lunar and interplanetary missions. However, NASAs Starlight program points a path forward to send small, relativistic spacecraft far outside our Solar System via standoff directed-energy propulsion. These miniaturized spacecraft are capable of robotic exploration but can also transport seeds and organisms, marking a profound change in our ability to both characterize and expand the reach of known life. Lantin et al. explore the biological and technological challenges of interstellar space biology, focusing on radiation-tolerant microorganisms capable of cryptobiosis. Image credit: University of California, Santa Barbara.

I think its our destiny to keep exploring, said Professor Rothman, a researcher in the Department of Molecular, Cellular and Developmental Biology at the University of California, Santa Barbara.

Look at the history of the human species. We explore at smaller and smaller levels down to subatomic levels and we also explore at increasingly larger scales.

Such drive toward ceaseless exploration lies at the core of who we are as a species.

The biggest challenge to human-scale interstellar travel is the enormous distance between Earth and the nearest stars.

NASAs Voyager missions have proven that we can send objects across the 19.3 billion km (12 billion miles) it takes to exit the bubble surrounding our Solar System, the heliosphere.

But the car-sized probes, traveling at speeds of more than 56,000 kmh (35,000 mph), took 40 years to reach there and their distance from Earth is only a tiny fraction of that to the next star. If they were headed to the closest star, it would take them over 80,000 years to reach it.

That challenge is a major focus of the teams work, in which they reimagine the technology it would take to reach the next Solar System in human terms.

Traditional onboard chemical propulsion is out; it cant provide enough energy to move the craft fast enough, and the weight of it and current systems needed to propel the ship are not viable for the relativistic speeds the craft needs to achieve.

New propulsion technologies are required and this is where the University of California, Santa Barbaras directed energy research program of using light as the propellant comes in.

This has never been done before, to push macroscopic objects at speeds approaching the speed of light, said Professor Lubin, a researcher in the Department of Physics at the University of California, Santa Barbara.

Mass is such a huge barrier, in fact, that it rules out any human missions for the foreseeable future.

As a result, the team turned to robots and photonics. Small probes with onboard instrumentation that sense, collect and transmit data back to Earth will be propelled up to 20-30% of the speed of light by light itself using a laser array stationed on Earth, or possibly the Moon.

We dont leave home with it. The primary propulsion system stays at home while spacecraft are shot out at relativistic speeds, Professor Lubin said.

The main propulsion laser is turned on for a short period of time and then the next probe is readied to be launched.

As the program evolves the spacecraft become larger with enhanced capability.

The core technology can also be used in a modified mode to propel much larger spacecraft within our Solar System at slower speeds, potentially enabling human missions to Mars in as little as one month, stopping included. This is another way of spreading life, but in our Solar System.

At these relativistic speeds roughly161 million kmh (100 million mph) the wafercraft would reach the next solar system, Proxima Centauri, in roughly 20 years.

Getting to that level of technology will require continuous innovation and improvement of both the space wafer, as well the photonics.

The basic project to develop a roadmap to achieve relativistic flight via directed energy propulsion is supported by NASA and private foundations such as the Starlight program and by the Breakthrough Initiatives as the Starshot program.

When I learned that the mass of these craft could reach gram levels or larger, it became clear that they could accommodate living animals, Professor Rothman said.

We realized that Caenorhabditis elegans could be the first Earthlings to travel between the stars. These intensively studied roundworms may be small and plain, but they are experimentally accomplished creatures.

Research on this little animal has led to Nobel prizes to six researchers thus far.

Caenorhabditis elegans are already veterans of space travel, as the subject of experiments conducted on the International Space Station and aboard the space shuttle, even surviving the tragic disintegration of the Columbia shuttle.

Among their special powers, which they share with other potential interstellar travelers that the authors study, tardigrades can be placed in suspended animation in which virtually all metabolic function is arrested.

Thousands of these tiny creatures could be placed on a wafer, put in suspended animation, and flown in that state until reaching the desired destination.

They could then be wakened in their tiny StarChip and precisely monitored for any detectable effects of interstellar travel on their biology, with the observations relayed to Earth by photonic communication.

We can ask how well they remember trained behavior when theyre flying away from their earthly origin at near the speed of light, and examine their metabolism, physiology, neurological function, reproduction and aging, Professor Rothman said.

Most experiments that can be conducted on these animals in a lab can be performed onboard the StarChips as they whiz through the cosmos.

The effects of such long odysseys on animal biology could allow the scientists to extrapolate to potential effects on humans.

We could start thinking about the design of interstellar transporters, whatever they may be, in a way that could ameliorate the issues that are detected in these diminutive animals.

The teams paper was published in the journal Acta Astronautica.

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Stephen Lantin et al. 2022. Interstellar space biology via Project Starlight. Acta Astronautica 190: 261-272; doi: 10.1016/j.actaastro.2021.10.009

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