Voyager 1, shown in this illustration, has operated for decades thanks to a radioisotope power system. NASA via APBenjamin Roulston, Clarkson University Powering spacecraft with solar energy may not seem like a challenge, given how intense the Sun’s light can feel on Earth. Spacecraft near the Earth use large solar panels to harness the Sun for the electricity needed to run their communications systems and science instruments. However, the farther into space you go, the weaker the Sun’s light becomes and the less useful it is for powering systems with solar panels. Even in the inner solar system, spacecraft such as lunar or Mars rovers need alternative power sources. As an astrophysicist and professor of physics, I teach a senior-level aerospace engineering course on the space environment. One of the key lessons I emphasize to my students is just how unforgiving space can be. In this extreme environment where spacecraft must withstand intense solar flares, radiation and temperature swings from hundreds of degrees below zero to hundreds of degrees above zero, engineers have developed innovative solutions to power some of the most remote and isolated space missions. So how do engineers power missions in the outer reaches of our solar system and beyond? The solution is technology developed in the 1960s based on scientific principles discovered two centuries ago: radioisotope thermoelectric generators, or RTGs. RTGs are essentially nuclear-powered batteries. But unlike the AAA batteries in your TV remote, RTGs can provide power for decades while hundreds of millions to billions of miles from Earth.
Nuclear power
Radioisotope thermoelectric generators do not rely on chemical reactions like the batteries in your phone. Instead, they rely on the radioactive decay of elements to produce heat and eventually electricity. While this concept sounds similar to that of a nuclear power plant, RTGs work on a different principle. Most RTGs are built using plutonium-238 as their source of energy, which is not usable for nuclear power plants since it does not sustain fission reactions. Instead, plutonium-238 is an unstable element that will undergo radioactive decay. Radioactive decay, or nuclear decay, happens when an unstable atomic nucleus spontaneously and randomly emits particles and energy to reach a more stable configuration. This process often causes the element to change into another element, since the nucleus can lose protons.Plutonium-238 decays into uranium-234 and emits an alpha particle, made of two protons and two neutrons.NASA When plutonium-238 decays, it emits alpha particles, which consist of two protons and two neutrons. When the plutonium-238, which starts with 94 protons, releases an alpha particle, it loses two protons and turns into uranium-234, which has 92 protons. These alpha particles interact with and transfer energy into the material surrounding the plutonium, which heats up that material. The radioactive decay of plutonium-238 releases enough energy that it can glow red from its own heat, and it is this powerful heat that is the energy source to power an RTG.The nuclear heat source for the Mars Curiosity rover is encased in a graphite shell. The fuel glows red hot because of the radioactive decay of plutonium-238.Idaho National Laboratory, CC BY
Heat as power
Radioisotope thermoelectric generators can turn heat into electricity using a principle called the Seebeck effect, discovered by German scientist Thomas Seebeck in 1821. As an added benefit, the heat from some types of RTGs can help keep electronics and the other components of a deep-space mission warm and working well. In its basic form, the Seebeck effect describes how two wires of different conducting materials joined in a loop produce a current in that loop when exposed to a temperature difference.The Seeback effect is the principle behind RTGs. Devices that use this principle are called thermoelectric couples, or thermocouples. These thermocouples allow RTGs to produce electricity from the difference in temperature created by the heat of plutonium-238 decay and the frigid cold of space.
Radioisotope thermoelectric generator design
In a basic radioisotope thermoelectric generator, you have a container of plutonium-238, stored in the form of plutonium-dioxide, often in a solid ceramic state that provides extra safety in the event of an accident. The plutonium material is surrounded by a protective layer of foil insulation to which a large array of thermocouples is attached. The whole assembly is inside a protective aluminum casing.An RTG has decaying material in its core, which generates heat that it converts to electricity.U.S. Department of Energy The interior of the RTG and one side of the thermocouples is kept hot – close to 1,000 degrees Fahrenheit (538 degrees Celsius) – while the outside of the RTG and the other side of the thermocouples are exposed to space. This outside, space-facing layer can be as cold as a few hundred degrees Fahrenheit below zero. This strong temperature difference allows an RTG to turn the heat from radioactive decay into electricity. That electricity powers all kinds of spacecraft, from communications systems to science instruments to rovers on Mars, including five current NASA missions. But don’t get too excited about buying an RTG for your house. With the current technology, they can produce only a few hundred watts of power. That may be enough to power a standard laptop, but not enough to play video games with a powerful GPU. For deep-space missions, however, those couple hundred watts are more than enough. The real benefit of RTGs is their ability to provide predictable, consistent power. The radioactive decay of plutonium is constant – every second of every day for decades. Over the course of about 90 years, only half the plutonium in an RTG will have decayed away. An RTG requires no moving parts to generate electricity, which makes them much less likely to break down or stop working. Additionally, they have an excellent safety record, and they’re designed to survive their normal use and also be safe in the event of an accident.
RTGs in action
RTGs have been key to the success of many of NASA’s solar system and deep-space missions. The Mars Curiosity and Perseverance rovers and the New Horizons spacecraft that visited Pluto in 2015 have all used RTGs. New Horizons is traveling out of the solar system, where its RTGs will provide power where solar panels could not. However, no missions capture the power of RTGs quite like the Voyager missions. NASA launched the twin spacecraft Voyager 1 and Voyager 2 in 1977 to take a tour of the outer solar system and then journey beyond it.The RTGs on the Voyager probes have allowed the spacecraft to stay powered up while they collect data.NASA/JPL-Caltech Each craft was equipped with three RTGs, providing a total of 470 watts of power at launch. It has been almost 50 years since the launch of the Voyager probes, and both are still active science missions, collecting and sending data back to Earth. Voyager 1 and Voyager 2 are about 15.5 billion miles and 13 billion miles (nearly 25 billion kilometers and 21 billion kilometers) from the Earth, respectively, making them the most distant human-made objects ever. Even at these extreme distances, their RTGs are still providing them consistent power. These spacecraft are a testament to the ingenuity of the engineers who first designed RTGs in the early 1960s. Benjamin Roulston, Assistant Professor of Physics, Clarkson University This article is republished from The Conversation under a Creative Commons license. Read the original article.
Unlikely Collaborators is bringing astrophysicist Dr. Lisa Kaltenegger to Santa Monica for a conversation centered on one of science’s most enduring questions: Are we alone in the universe? The event, part of the organization’s Spark Salon series, took place on March 17 at 7:00 p.m. PT and was offered both in person and via livestream.
Kaltenegger, founding director of the Carl Sagan Institute at Cornell University and a professor of astronomy, is widely recognized for her work on habitable exoplanets and the search for detectable signs of life beyond Earth. Her talk focused not only on the science of planet hunting, but also on the assumptions people bring to questions about life, habitability, and reality itself.On March 17 at 7 PM PT, Unlikely Collaborators hosts Cornell astronomer and Carl Sagan Institute Founding Director Dr. Lisa Kaltenegger for Spark Salon: Are We Alone in the Universe? Explore the search for life on distant worlds and the deeper question of how our assumptions shape what we recognize as life, reality, and possibility. In person in Santa Monica + livestream.
According to the event announcement, the discussion examined how scientists interpret data from distant worlds and asked broader questions about what counts as life, what makes a planet habitable, and how human perspective can shape discovery. The program also highlighted how the search for life beyond Earth can challenge long-held ideas about what is normal, possible, and even alive.
The evening included a reception, the main program, and a book signing. In-person guests also received a complimentary copy of Kaltenegger’s book, Alien Earths: The New Science for Planet Hunting in the Cosmos.
Unlikely Collaborators, founded by Elizabeth R. Koch, describes itself as a nonprofit focused on helping people better understand themselves and the world through its Perception Box framework. The Spark Salon series regularly brings together researchers, artists, and thought leaders for conversations designed to challenge perspective and encourage reflection.
Dive into “The Knowledge,” where curiosity meets clarity. This playlist, in collaboration with STMDailyNews.com, is designed for viewers who value historical accuracy and insightful learning. Our short videos, ranging from 30 seconds to a minute and a half, make complex subjects easy to grasp in no time. Covering everything from historical events to contemporary processes and entertainment, “The Knowledge” bridges the past with the present. In a world where information is abundant yet often misused, our series aims to guide you through the noise, preserving vital knowledge and truths that shape our lives today. Perfect for curious minds eager to discover the ‘why’ and ‘how’ of everything around us. Subscribe and join in as we explore the facts that matter. https://stmdailynews.com/the-knowledge/
How extraterrestrial tales of aliens gain traction
The narrative explores humanity’s intrigue with extraterrestrial entities, juxtaposing evolutionary processes with claims of alien interventions, ultimately emphasizing the need for scientific evidence over fantastical stories. Aliens!
One night, upon returning to the cave that his tribe calls home, the monkey-humanoid Moon-Watcher finds a strange crystal object, a kind of monolith that fascinates him at first, but then quickly loses his interest when he discovers that it is not edible. Soon after, the true purpose of the monolith is revealed to be none other than penetrating the minds of our ancestors to induce new abilities that, over time, will cause the development of an intelligence capable of creating new technology.
Many readers will recognise this scene from the novel 2001, A Space Odyssey, by Arthur C. Clarke, and the film of the same name, directed by Stanley Kubrick. It almost goes without saying that the crystal monolith in question is the work of an extraterrestrial civilisation that observes life on other planets and “experiments” on them to encourage the development of intelligence in as many parts of the cosmos as possible.
Seeking simple answers to complex questions
Understanding how we, as a species, came to be intelligent is one of the great enigmas of evolutionary study. Small mutations, followed by a process of natural selection to choose the most advantageous, seems too slow a process for structures as complex as the human nervous system or brain to emerge. It is this very complexity that allows millions of neurons to communicate with each other, resulting in the emergence of qualities such as the ability to respond voluntarily to environmental stimuli, or to ask questions about the very nature of humankind and the universe.
This has always been the case, in all human cultures. A classic example would be attributing atmospheric events – thunder, lightning, floods – to the wrath of God. These ideas came about before humans had ever left the ground, so it is no surprise that we turned our eyes even higher – to extraterrestrials – to explain other phenomena that we could only observe once travelling at high altitudes became part of our daily lives.
The allure of the unknown
The possibility that we might have been visited by beings from other worlds has always fascinated us. The element of mystery, of the unknown, only makes it more interesting.
Any phenomenon is made all the more enticing when it seems it is being covered up or hidden for secretive reasons. The attractiveness of conspiracies often leads people towards ideas which have no scientific basis, such as the belief that the Earth is flat, that humans never set foot on the Moon, or that vaccines can control our behaviour.
Even though these ideas have repeatedly been shown to be untrue, their rapid dissemination through social media, using simple, blunt language that appeals to emotion over logic, makes them very powerful weapons.
The supposed “proof” of alien visits to our planet ranges from specific Bible passages to ancient stone carvings portraying creatures or objects that may appear to be aliens or spacecraft. The latter often take the form of flying saucers.
However, we cannot forget that humans have always created imaginary creatures that resemble them and attributed them with magical powers. When imagining Gods, humans have given them a human appearance, and almost always imagined them as living in the sky.
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When we look at these representations through modern eyes, we associate them with extraterrestrial beings or structures, when in fact they could be referring to a range of different things.
What we can be certain of is that the more we explore our skies, the more likely it is that we will encounter phenomena that we cannot explain. However, this does not mean that they are extraterrestrial. Past experience has shown us that most of these events can be attributed to optical illusions, spy or weather balloons, space junk, or even satellites that we ourselves have made.
In Spain, UFOs were a hot topic between the 1960s and the 1980s. In this era, everyone knew someone who was convinced that they had seen a UFO. This even reached the point where an exoplanet, called Ummo, was made up. It was populated by a more advanced civilisation than ours who made contact with people on Earth. In the letters these aliens supposedly sent, the ‘Ummites’ explained concepts such as genetics and cell structure.
The Ummo hoax was even linked to the creation of a paedophile ring, which should make us reflect on the harmful consequences that the spread of fabricated news stories can have.
Can we deny the possibility that intelligent alien civilisations exist?
The answer, of course, is no. The universe is immense, and it is more than likely that circumstances similar to those which led to the appearance of life on Earth have been repeated on other planets. But there is a huge distance (literally and figuratively) between acknowledging the existence of these creatures and considering the possibility that they might have visited us.
Exoplanets, also known as extrasolar planets, are extremely far away, and we are limited by the speed of light which, as proven by Einstein, is the maximum possible speed at which anything can travel. Therefore, the journey to even a “nearby” exoplanet would take thousands of years. Maybe a civilisation more advanced than ours could find a way to do it faster, but not to the point of it being something easy or commonplace.
In any case, if the remains of alien life or spacecraft are stored away somewhere, why are they not being shown to us? Scientists would jump at the chance to analyse this organic matter to find out how it is structured, how it metabolises energy, or what molecules it uses to store genetic information.
Until there is proof, this is not a question of science, but rather, of stories. Stories can be very entertaining, but these kinds of stories do not help us to build a more accurate or helpful view of the world.
The science section of our news blog STM Daily News provides readers with captivating and up-to-date information on the latest scientific discoveries, breakthroughs, and innovations across various fields. We offer engaging and accessible content, ensuring that readers with different levels of scientific knowledge can stay informed. Whether it’s exploring advancements in medicine, astronomy, technology, or environmental sciences, our science section strives to shed light on the intriguing world of scientific exploration and its profound impact on our daily lives. From thought-provoking articles to informative interviews with experts in the field, STM Daily News Science offers a harmonious blend of factual reporting, analysis, and exploration, making it a go-to source for science enthusiasts and curious minds alike. https://stmdailynews.com/category/science/
We’re only halfway through 2023, and it feels already like the year of alien contact.
In February, President Joe Biden gave orders to shoot down three unidentified aerial phenomena – NASA’s title for UFOs. Then, the alleged leaked footage from a Navy pilot of a UFO, and then news of a whistleblower’s report on a possible U.S. government cover-up about UFO research. Most recently, an independent analysis published in June suggests that UFOs might have been collected by a clandestine agency of the U.S. government.
If any actual evidence of extraterrestrial life emerges, whether from whistleblower testimony or an admission of a cover-up, humans would face a historic paradigm shift.
As members of an Indigenous studies working group who were asked to lend our disciplinary expertise to a workshop affiliated with the Berkeley SETI Research Center, we have studied centuries of culture contacts and their outcomes from around the globe. Our collaborative preparations for the workshop drew from transdisciplinary research in Australia, New Zealand, Africa and across the Americas.
In its final form, our group statement illustrated the need for diverse perspectives on the ethics of listening for alien life and a broadening of what defines “intelligence” and “life.” Based on our findings, we consider first contact less as an event and more as a long process that has already begun.
Who’s in charge of first contact
The question of who is “in charge” of preparing for contact with alien life immediately comes to mind. The communities – and their interpretive lenses – most likely to engage in any contact scenario would be military, corporate and scientific.
By giving Americans the legal right to profit from space tourism and planetary resource extraction, the Commercial Space Launch Competitiveness Act of 2015 could mean that corporations will be the first to find signs of extraterrestrial societies. Otherwise, while detecting unidentified aerial phenomena is usually a military matter, and NASA takes the lead on sending messages from Earth, most activities around extraterrestrial communications and evidence fall to a program called SETI, or the search for extraterrestrial intelligence.
SETI investigators are virtually always STEM – science, technology, engineering and math – scholars. Few in the social science and humanities fields have been afforded opportunities to contribute to concepts of and preparations for contact.
In a promising act of disciplinary inclusion, the Berkeley SETI Research Center in 2018 invited working groups – including our Indigenous studies working group – from outside STEM fields to craft perspective papers for SETI scientists to consider.
Ethics of listening
Neither Breakthough Listen nor SETI’s site features a current statement of ethics beyond a commitment to transparency. Our working group was not the first to raise this issue. And while the SETI Institute and certain research centers have included ethics in their event programming, it seems relevant to ask who NASA and SETI answer to, and what ethical guidelines they’re following for a potential first contact scenario.
SETI’s Post-Detection Hub – another rare exception to SETI’s STEM-centrism – seems the most likely to develop a range of contact scenarios. The possible circumstances imagined include finding ET artifacts, detecting signals from thousands of light years away, dealing with linguistic incompatibility, finding microbial organisms in space or on other planets, and biological contamination of either their or our species. Whether the U.S. government or heads of military would heed these scenarios is another matter.
SETI-affiliated scholars tend to reassure critics that the intentions of those listening for technosignatures are benevolent, since “what harm could come from simply listening?” The chair emeritus of SETI Research, Jill Tarter, defended listening because any ET civilization would perceive our listening techniques as immature or elementary.
But our working group drew upon the history of colonial contacts to show the dangers of thinking that whole civilizations are comparatively advanced or intelligent. For example, when Christopher Columbus and other European explorers came to the Americas, those relationships were shaped by the preconceived notion that the “Indians” were less advanced due to their lack of writing. This led to decades of Indigenous servitude in the Americas.This 16th century engraving shows Christopher Columbus landing in the Americas, where he and his explorers deemed the Indigenous people there as ‘primitive,’ as they had no writing system. Theodor de Bry/Wikimedia Commons
The working group statement also suggested that the act of listening is itself already within a “phase of contact.” Like colonialism itself, contact might best be thought of as a series of events that starts with planning, rather than a singular event. Seen this way, isn’t listening potentially without permission just another form of surveillance? To listen intently but indiscriminately seemed to our working group like a type of eavesdropping.
It seems contradictory that we begin our relations with aliens by listening in without their permission while actively working to stop other countries from listening to certain U.S. communications. If humans are initially perceived as disrespectful or careless, ET contact could more likely lead to their colonization of us.
Histories of contact
Throughout histories of Western colonization, even in those few cases when contactees were intended to be protected, contact has led to brutal violence, pandemics, enslavement and genocide.
James Cook’s 1768 voyage on the HMS Endeavor was initiated by the Royal Society. This prestigious British academic society charged him with calculating the solar distance between the Earth and the Sun by measuring the visible movement of Venus across the Sun from Tahiti. The society strictly forbade him from any colonial engagements.
Though he achieved his scientific goals, Cook also received orders from the Crown to map and claim as much territory as possible on the return voyage. Cook’s actions put into motion wide-scale colonization and Indigenous dispossession across Oceania, including the violent conquests of Australia and New Zealand.
The Royal Society gave Cook a “prime directive” of doing no harm and to only conduct research that would broadly benefit humanity. However, explorers are rarely independent from their funders, and their explorations reflect the political contexts of their time.
As scholars attuned to both research ethics and histories of colonialism, we wrote about Cook in our working group statement to showcase why SETI might want to explicitly disentangle their intentions from those of corporations, the military and the government.
Although separated by vast time and space, both Cook’s voyage and SETI share key qualities, including their appeal to celestial science in the service of all humanity. They also share a mismatch between their ethical protocols and the likely long-term impacts of their success. https://www.youtube.com/embed/5gZwLGrJQrM?wmode=transparent&start=0 This BBC video describes the modern ramifications of Captain James Cook’s colonial legacy in New Zealand.
The initial domino of a public ET message, or recovered bodies or ships, could initiate cascading events, including military actions, corporate resource mining and perhaps even geopolitical reorganizing. The history of imperialism and colonialism on Earth illustrates that not everyone benefits from colonization. No one can know for sure how engagement with extraterrestrials would go, though it’s better to consider cautionary tales from Earth’s own history sooner rather than later.
This article has been updated to correct the date of James Cook’s voyage.
The science section of our news blog STM Daily News provides readers with captivating and up-to-date information on the latest scientific discoveries, breakthroughs, and innovations across various fields. We offer engaging and accessible content, ensuring that readers with different levels of scientific knowledge can stay informed. Whether it’s exploring advancements in medicine, astronomy, technology, or environmental sciences, our science section strives to shed light on the intriguing world of scientific exploration and its profound impact on our daily lives. From thought-provoking articles to informative interviews with experts in the field, STM Daily News Science offers a harmonious blend of factual reporting, analysis, and exploration, making it a go-to source for science enthusiasts and curious minds alike. https://stmdailynews.com/category/science/
