Levende, groeiende gebouwen: gaan we onze eerste Marskolonie bouwen met de hulp van algen?

 Jeannette Kras - Redacteur

Als mensen ooit echt op Mars willen wonen, dan moeten we eerst een oplossing vinden voor een gigantisch probleem: hoe bouw je een leefbare omgeving zonder duizenden en duizenden kilo’s aan bouwmateriaal vanaf de Aarde te verschepen? Dit is peperduur en logistiek bijna onmogelijk. Maar de redding komt misschien wel uit onverwachte hoek…

Onderzoekers van de Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) denken een oplossing te hebben gevonden in de levende natuur en schrijven erover in de nieuwste uitgave van het vakblad Science Advances. Hoofdonderzoeker Robin Wordsworth laat zien dat het mogelijk is om groene algen te laten groeien in bunkers gemaakt van bioplastic, onder omstandigheden die lijken op wat het oppervlak van Mars te bieden heeft. Het is een veelbelovende stap richting het bouwen van duurzame buitenaardse huizen die zichzelf kunnen onderhouden en nog kunnen groeien ook.

Bizarre omstandigheden
In het lab bootste het onderzoeksteam de ijle atmosfeer van Mars na: een druk van 600 Pascal (dat is meer dan honderd keer lager dan op Aarde) en een omgeving rijk aan koolstofdioxide in plaats van alle stikstof en zuurstof waar onze atmosfeer vol mee zit. Onder die bizarre omstandigheden slaagden ze erin om de algensoort Dunaliella tertiolecta te laten groeien in een speciaal ontworpen, 3D-geprinte kamer gemaakt van het bioplastic polymelkzuur (in het Engels bekend als polylactic acid (PLA)). Deze stof is een biologisch afbreekbaar en composteerbaar plastic gemaakt van maïszetmeel, suikerriet of tapioca. Het wordt vaak gebruikt als een duurzaam alternatief voor traditionele plastics, vooral bij 3D-printen, voedselverpakkingen en medische implantaten.

De bioplastickamer heeft meerdere functies: hij laat genoeg licht door om de algen te laten fotosynthetiseren, houdt schadelijke UV-straling buiten en zorgt voor een drukverschil waardoor water – ondanks de lage luchtdruk – vloeibaar blijft. “Als je een habitat hebt gemaakt van bioplastic en je laat daar algen in groeien, dan kunnen die algen weer nieuw bioplastic produceren”, legt Wordsworth uit. “Zo krijg je een soort zelfvoorzienend systeem dat nog lang door kan blijven groeien, ook als het bouwwerk al lang en breed staat.”

Bioplastic met algengroei. Foto: Wordsworth Group / Harvard SEAS

Een leefbare bubbel op een dode planeet
Tot nu toe waren plannen voor leven op Mars vooral gericht op industriële technieken, oftewel dure materialen produceren en met veel moeite recyclen. Het idee van Wordsworth is veel natuurlijker; het is een systeem dat werkt zoals de ecosystemen op Aarde. Het team werkte eerder ook al aan lokale ’terraforming’ van Mars: met behulp van aerogel – een superlicht en isolerend materiaal – creëerden ze een soort kaseffect dat de bodem opwarmde, zodat er planten konden groeien. Combineer je die technologie met deze nieuwe bioplastic-algenkamers, dan krijg je een leefbare omgeving waarin druk en temperatuur onder controle blijven.

Levende, groeiende gebouwen
Wordsworth en zijn collega’s zijn al druk bezig met de volgende stap. Ze gaan de nieuwste versie van hun habitats testen onder vacuümomstandigheden, zoals het er op de maan of in de ruimte aan toegaat. Ook zijn er plannen om een volledig werkend ‘closed loop-systeem’ te bouwen: een leefruimte die zichzelf in stand houdt en zelfs nieuwe onderdelen kan produceren. “Het idee van habitats die opgebouwd zijn uit biologische materialen is niet alleen fascinerend, het is ook haalbaar”, zegt Wordsworth. “En als het lukt om deze technologie verder te ontwikkelen, dan kunnen we die misschien ook op Aarde gebruiken voor een duurzamer manier van bouwen.”

Bronmateriaal

• "Biomaterials for organically generated habitats beyond Earth" - Science
  
• Afbeelding bovenaan dit artikel: Mars

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{ https://scientias.nl/nieuws/astronomie-ruimtevaart/ }

Report: Over 2,000 UFO Sightings in First Half of 2025

The National UFO Reporting Center has received more than 2,000 incidents of UFO sightings in the first half of 2025, The Hill reported Friday.

Since January, the nonprofit, known as NUFORC, has received 2,174 reports of UFOs and unexplained sightings in 2025, an increase from the 1,492 over the same period in 2024.

The center, which has collected and investigated cases since 1974, noted that of the 3,000 reports collected this year, many of the sightings happened years or decades ago and are not immediately reported due to the stigma involving UFO cases.

Christian Stepien, NUFORC's chief technology officer, said he believes that only 5% of sightings are ever reported. Over the years, the center has received information from air traffic controllers, military personnel, police, and everyday citizens.

"There are so many things being seen by so many people. And if it's a secret block project, you're not flying it over highly populated neighborhoods where everybody can see it, and even these days, have pictures of it," Stepien told the outlet.

Many of the cases NUFORC received end up being easily explained as balloons, drones, planets, and stars.

"We get lots of reports of balloons and things like that that we can say that's clearly a balloon, or that's a drone, or it's an airplane or whatever it is," he said. Roughly 3% of the reports turn out to be worth pursuing.

"The dramatic ones are kind of the cases where you say somebody saw a giant triangle floating over their house the size of a tennis court or a football field," Stepien said. "And we get those reports fairly regularly, things that can't possibly be mistaken for something else."

The report from NUFORC comes as the Trump administration seeks to be more transparent about UFOs. The White House announced in June an order to "restore American airspace sovereignty."

The task force recognizes the growing threat of unmanned aircraft systems and seeks to increase restrictions over critical infrastructure and develop new drone detection technologies. Stepien hopes the new attitude toward UFOs from the government will strengthen these efforts.

"The government certainly has the good stuff," he added. "These days with cellphones and things like that, we're starting to get some nice videos and things, but we don't have high-resolution cameras and forward-looking infrared [technology] and that kind of stuff."

Related Stories:

• WSJ Throws Cold Water on UFOs
• Story of Interdimensional Doorway Near Area 51 Resurfaces

{ https://www.newsmax.com/ }

 By Sarah Rumpf-Whitten Fox News

UFO appears to disappear in the water without making a splash

An Unidentified Anomalous Phenomena (UAP) was filmed from the USS Omaha off coast of San Diego in July 2019. CREDIT: Jeremy Corbell/WeaponizedPodcast

New York state has seen 66 reported Unidentified Aerial Phenomena (UAP) sightings during the first half of 2025, according to a report from the National UFO Reporting Center (NUFORC).

With 66 distinct incidents logged between January and late June, the state has had reports of an array of mysterious aerial objects, ranging from glowing orbs and silent triangles to fast-moving disks and shape-shifting lights.

The incidents, according to NUFORC, span rural hamlets, suburban skies and the bustling airspace of the Big Apple.

The NUFORC had 65 reported UFO sightings in New York in the first half of 2024.

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The phenomenon appears to be statewide, with hot spots in urban centers like New York City as well as multiple reports from smaller towns such as Chester, Ridge and Evans Mills. 

Evans Mills, which is located near a military base, saw repeated orb sightings in March, prompting witness speculation about possible connections to defense activities. 

The most common shapes were orbs, spheres and triangles, frequently observed performing advanced maneuvers.

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Several reports detailed sharp right-angle turns, sudden accelerations and zigzagging flight paths. 

One particularly vivid sighting, according to NUFORC, took place in Chester on March 25, 2025, when someone walking their dog around 6 p.m. reported seeing two extremely fast white orbs flying in close formation.

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Initially, the witness believed the objects to be birds, but their unusual speed and synchronized, wavering flight pattern stood out. Midway through their trajectory across the sky, the objects executed a sharp, nearly 90-degree turn to the northwest without any deceleration, the witness claimed. 

At that moment, they transformed into dark, aerodynamic ovals that nearly disappeared into the night sky, according to the report. The witness described the orbs as momentarily pitch black.

A handful of these sightings also included photographic or video evidence, although NUFORC has not released digital evidence.

Other entries speculated about plausible explanations, like drones, aircraft, fireworks and even the International Space Station. The bulk of reports from NUFORC remain open and unexplained.

April through June represented a peak in activity, aligning with warmer months that typically encourage outdoor observations.

Another remarkable incident reportedly occurred on June 24, 2025, during a commercial flight approaching New York City. 

A passenger seated in 1A reported to NUFORC that they witnessed a metallic ball flying in the opposite direction, roughly 100 to 200 feet below the aircraft. 

The witness, arriving from Toronto, described the object as a perfectly round, shiny sphere that caught his eye due to its metallic gleam. 

The witness noted that the object did not resemble a balloon or stationary object, saying it moved steadily away from the aircraft. 

The passenger immediately alerted the pilots upon landing, though neither reported seeing the object. Despite this, the observer remained convinced of the object’s extraordinary nature.

WATCH: These states are best prepared for alien invasion, UFO expert says

NUFORC was founded in 1974 by UFO investigator Robert J. Gribble and aims to document and investigate unexplained sightings across the world.

"The Center’s primary function over the past five decades has been to receive, record, and to the greatest degree possible, corroborate and document reports from individuals who have been witness to unusual, possibly UFO-related events," the website says.

{ https://www.foxnews.com/ }

Declassified documents revealing a United States military aircraft was previously struck by an unknown flying object is raising eyebrows as experts point to other unexplainable sightings suggesting otherworldly technology flying within the country’s airspace. 

The incident occurred in January 2023, after an unidentified object collided with the left side of an F-16 Viper jet participating in training exercises near Gila Benda, Arizona, an Air Force spokesperson confirmed to Fox News Digital. 

The flying object struck the clear "canopy" at the top of the aircraft and was first spotted by an instructor pilot sitting in the rear of the plane, officials said. An initial investigation determined no damage was done to the near $70 million jet, with officials ruling against a possible bird strike. 

• OVER 60 UFO SIGHTINGS REPORTED WHIZZING ACROSS STATE IN FIRST HALF OF 2025, NATIONAL TRACKING GROUP SAYS

Authorities ultimately determined the aircraft was struck by a drone, but the location and operator of the device have yet to be determined, the spokesperson said. 

The incident was the first of four encounters with unidentified anomalous phenomena (UAP) that were reported a day later, according to Federal Aviation Administration (FAA) documents obtained by the War Zone. 

"According to military personnel I’ve personally met with, there were objects 200 miles off the East Coast that were extensively loitering and had no visible means of propulsion," James Fox, a director specializing in films about UFO activity, told Fox News Digital. "So a report from 2023 about an actual impact with a UAP doesn’t really surprise me." 

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The concerning collision comes as the Department of Defense reported 757 incidents involving UAPs from May 1, 2023, to June 1, 2024, according to an unclassified document released by the All-Domain Anomaly Resolution Office. 

Of those encounters, 708 occurred in the air, with only 49 instances marked as "case closed" by officials. Additionally, the department received 18 reports regarding UAP incidents near nuclear infrastructure, launch sites and weapons, according to the report.

"None of these resolved cases substantiated advanced foreign adversarial capabilities or breakthrough aerospace technologies," the report states. 

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The sightings of UAPs near military sites are nothing new, according to Fox. 

"There are reports dating back to the 1930s and 1940s," Fox said. "Where you had mysterious, glowing, and orb-like objects that emitted very bright light that could just fly rings around the military planes from World War II."

Fox pointed to the sheer advanced technology showcased within these sightings, such as aircraft that do not emit a heat signature or have the ability to fly stationary in high wind conditions.

"This has been well-documented for decades," Fox said. "So either we’ve managed to track the same thing it’s been, [possibly] non-human intelligence, since the 1940s. Or someone has managed to replicate the technology, reverse engineer it and they’re flying it around." 

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{ https://www.foxnews.com/  }

Life on Mars could survive — so long as you're one of these strange, hybrid lifeforms

One group of living things that may be able to survive these extreme conditions is lichens, symbiotic associations between fungi and photosynthetic bacteria and/or algae. These hybrid lifeforms, which are not considered true organisms but are listed as species on the three of life, work together to stay alive and many are extremophiles, capable of tolerating no hydration and extreme temperatures for long periods. Some species have even survived being directly exposed to the vacuum of space.

In the new study, published March 31 in the journal IMA Fungus, researchers tested how two lichen species — Diploschistes muscorum and Cetraria aculeata — reacted to ionizing radiation under Martian conditions. To do this, the team placed the lifeforms in a specialized vacuum chamber at the Space Research Centre of the Polish Academy of Sciences in Warsaw, which replicated the atmospheric pressure, temperatures and composition on the Red Planet. They bombarded the lichens with a year's worth of Martian radiation in just 5 hours. Both species were able to remain metabolically active throughout the tests.

Related: 

• Which animals will be the first to live on the moon and Mars?

"These findings expand our understanding of biological processes under simulated Martian conditions and reveal how hydrated organisms respond to ionizing radiation," Kaja Skubała, a researcher at the Institute of Botany at the Jagellonian University in Krakow, Poland, said in a statement. "Ultimately, this research deepens our knowledge of lichen adaptation and their potential for colonizing extraterrestrial environments."

Of the two species, D. muscorum showed the greatest resistance to the radiation, sustaining less damage to its cells, which suggests that some lichens will be better suited to Martian conditions than others. However, it is unlikely that any species would be able to survive on Mars unattended for long periods, as there is no known liquid water at the surface, which all of Earth's lifeforms need to survive.

This is the reason why it is unlikely that there is any extraterrestrial life currently alive on Mars.

Martian candidates

According to the researchers, the new experiments show that lichens are prime candidates for being taken on future Mars missions, although there are several resilient species other than D. muscorum that could also make the trip.

But lichens are not the only lifeforms that could potentially survive on the Red Planet.

One extremophile group that has long been considered as future Martian tourists is tardigrades. These microscopic critters are nearly indestructible and can survive extreme temperatures, crushing pressures, total dehydration and the vacuum of space, largely thanks to an ability to switch off their metabolism and enter a state of suspended animation.

Other candidates include mosses — plants with similar abilities to lichens. Some desert moss species have even been shown to be resilient to gamma rays and liquid nitrogen, hinting that they too could fare well on Mars.

Single-celled microorganisms, such as bacteria, might also be able to survive on Mars if they were sheltered from radiation, living underground. Research has shown that these microbes could also survive for hundreds of millions of years beneath the surface in a hibernation-like state.

However, the first terrestrial lifeforms to touch down on Mars will likely be a species that is naturally very poorly suited to living on Mars — humans. NASA intends on launching the first crewed mission to the Red Planet sometime in the 2030s, when they will get a taste of how tough it is to survive there.

• Editor's note: This article was originally published April 8, 2025

{ https://www.livescience.com/space }

Could signs of Mars life be hidden in its thick layers of clay?

"If you have stable terrain, you're not messing up your potentially habitable environments," Moore added. "Favorable conditions might be able to be sustained for longer periods of time."

On our home planet, such deposits form under specific landscape and climatic conditions.

"On Earth, the places where we tend to see the thickest clay mineral sequences are in humid environments, and those with minimal physical erosion that can strip away newly created weathering products," said co-author Tim Goudge, an assistant professor at the Jackson School's Department of Earth and Planetary Sciences.

Related: 

• Why does Mars look purple, yellow and orange in ESA's stunning new satellite image?

However, it remains unclear how Mars' local and global topography, along with its past climate activity, influenced surface weathering and the formation of clay layers.

Using data and images from NASA's Mars Reconnaissance Orbiter — the second-longest-operating spacecraft around Mars, after the agency's 2001 Mars Odyssey — Moore, Goudge, and their colleagues studied 150 clay deposits, looking at their shapes and locations, and how close they are to other features like ancient lakes or rivers.

They found that the clays are mostly located in low areas near ancient lakes, but not close to valleys where water once flowed strongly. This mix of gentle chemical changes and less intense physical erosion helped the clays stay preserved over time.

"[Clay mineral-bearing stratigraphies] tend to occur in areas where chemical weathering was favoured over physical erosion, farther from valley network activity and nearer standing bodies of water," the team wrote in the new study, which was published in the journal Nature Astronomy on June 16.

The findings suggest that intense chemical weathering on Mars may have disrupted the usual balance between weathering and climate.

On Earth, where tectonic activity constantly exposes fresh rock to the atmosphere, carbonate minerals like limestone form when rock reacts with water and carbon dioxide (CO2). This process helps remove CO2 from the air, storing it in solid form and helping regulate the climate over long periods.

On Mars, tectonic activity is non-existent, leading to a lack of carbonate minerals and minimal removal of CO2 from the planet's thin atmosphere. As a result, CO2 released by Martian volcanoes long ago likely stayed in the atmosphere longer, making the planet warmer and wetter in the past — conditions the team believes may have encouraged the clay's formation.

The researchers also speculate that the clay could have absorbed water and trapped chemical byproducts like cations, preventing them from spreading and reacting with the surrounding rock to form carbonates that remain trapped and unable to leech into the surrounding environment.

"[The clay is] probably one of many factors that's contributing to this weird lack of predicted carbonates on Mars," said Moore.

• This article was originally published on Space.com.

{ https://www.livescience.com/space }

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{ https://www.universetoday.com/ }

Aliens: Facts about extraterrestrial life and how scientists are looking for it

By Stephanie Pappas 

Discover interesting facts about where alien life forms are likely to exist, and what they look like.

(Image credit: KTSDESIGN/SCIENCE PHOTO LIBRARY via Getty Images)

Quick facts about aliens

• Has extraterrestrial life been discovered?: Not yet!
• Where are scientists looking for aliens?: Water-rich bodies in our solar system, like Jupiter's moon Europa, and Earth-like exoplanets — planets outside our solar system
• How many planets in the Milky Way have the right conditions for life? An estimated 300 million

E.T., Stitch, Chewbacca, Groot — humans have a lot of ideas about what aliens might look like. But what is the science behind extraterrestrial life? Is it possible that humans will ever experience "first contact" with an alien species?

Many scientists hope so. They're looking for extraterrestrial life on planets with conditions that look like Earth's. A life-friendly planet would probably have water, for example. And for water to be a liquid, the planet must be the perfect distance from its sun for that water not to freeze or turn into a gas.

There's no evidence yet for life on other planets, but as scientists discover more and more planets outside our solar system, they're hopeful that some of these worlds will be "just right" for life to exist or evolve there.

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5 fast facts about aliens

• Scientists have been listening for alien signals with special radio receivers since 1992. They haven't picked up any yet!
• Mars might have once hosted life — most likely tiny things like bacteria — but scientists can't say for sure.
• Jupiter's moon Europa has an ocean, and it might have hydrothermal vents, or cracks in the seafloor where hot water seeps through. Scientists think life on Earth may have evolved in hydrothermal vents.
• The "Goldilocks zone" is the space around a star where temperatures allow liquid water to exist. Many scientists think planets in the Goldilocks zone are those most likely to host life.
• The oldest known life on Earth is 4.2 billion years old.

Everything you need to know about aliens

Are aliens real?

Sci-fi aliens like Baby Yoda are fun to imagine, but scientists are serious about extraterrestrial life. There are some 100 billion stars in the Milky Way galaxy and at least 2 trillion galaxies in the universe we can study. If most of those stars have at least one planet around them, there could be up to 20 billion trillion extraterrestrial worlds out there.

Given those numbers, it would be shocking if only a single planet — Earth — had life. But our closest neighbors in the solar system, Mars and Venus, don't seem to have any life. Some moons of Saturn and Jupiter have water, so they could have life — most likely tiny creatures the size of germs. If Earthlings ever meet aliens face-to-face, they'll probably need a microscope to say hi.

Until scientists find some firm proof, such as a communication signal from an alien world or fossilized microbes from Mars, Earth remains the only planet where life is known to exist.

What might aliens look like?

What aliens would look like would depend on where they came from. For example, on the icy moons in our solar system (Jupiter's Ganymede and Europa, and Saturn's Enceladus), life could thrive around hydrothermal vents in the oceans under the ice. This life might look like the weird creatures of the deep ocean seen on Earth. There could be primitive microbes, like Earth's single-celled Archaea. There might be relatively simple creatures with many cells in their body, sort of like Earth's tube worms, which live off chemicals from the vent fluid.

Earth formed about 4.5 billion years ago, and we think the first life existed by about 4.2 billion years ago. But life on Earth started simple and stayed that way for a long time. The first microbes that produced carbon evolved at least 3.7 billion years ago. (Carbon is an element that is a part of all known life.) But the kind of cells that gave rise to animals, plants and other complex life-forms didn't evolve until between 2.7 billion and 1.8 billion years ago. Life-forms made of many cells didn't show up until 600 million years ago. And modern humans came on the scene only around 300,000 years ago.

That means that, if other planets with life are like Earth, the time period in which they might host intelligent life (or even something as cuddly as a koala) is pretty brief. But there's a good chance that human life might overlap with microbial life on another planet.

Scientists do think that life on other planets would be driven by the same processes as it is on Earth, namely evolution. Changes to the environment drive living things to change, leading to new and more complex species. So a planet out in space that is like Earth and has been through many changes in its surface, rocks and climate would probably have complex life, too. In that case, aliens might face similar challenges and needs as here on Earth, and thus might evolve similar features. Eyes, for example, have evolved independently dozens of times on Earth, and they might evolve in life on other planets, too.

Superpowerful telescopes are allowing researchers to detect planets beyond our solar system that might host life. This image shows some exoplanets that might be similar to Earth (from left to right): Kepler-22b, Kepler-69c, Kepler-452b, Kepler-62f and Kepler-186f. Earth is on the far right.  (Image credit: NASA/Ames/JPL-Caltech)

Where might aliens live?

Some scientists still hold out hope that life exists elsewhere in our solar system. If it does, it's probably on one of the these moons:

• Ganymede: Jupiter's largest moon is bigger than Mercury and hides a giant ocean under its icy surface.
• Europa: Another moon of Jupiter with an ice-bound ocean, Europa has liquid water, heat generated by the pull of Jupiter's gravity, and chemicals that are the building blocks of life.
• Enceladus: This Saturn moon spews water vapor that contains carbon compounds from its surface. One of these compounds, hydrogen cyanide, is important for the origin of life.
• Titan: This moon of Saturn is very cold, but it does have carbon-rich liquid on its surface. Any life found on Titan would have to thrive in conditions not seen on Earth.
• Triton: Neptune's moon Triton is very, very cold, but it might have an ocean under its surface layer of ice. It also has geological activity in the form of geysers that erupt when the sun heats the nitrogen ice on the planet's surface.

And our next-door neighbor, Mars, may have hosted life in the past, because it used to have liquid water and an atmosphere. Today, any life would have to persist in deep pools of water below the Red Planet's surface.

Outside the solar system, scientists are continually discovering new exoplanets. They can learn things about these planets' atmospheres by studying the types of light waves they see using superpowerful telescopes. One promising exoplanet for life is called K2-18b. This world is too far for humans to visit, but the light from the planet has reached Earth. This light tells us the planet has an ocean. Scientists think they've detected some chemicals in K2-18b's atmosphere that could be made by marine life, but they don't know for sure.

How are scientists looking for aliens?

Scientists look for aliens in a few different ways.

First, they listen for alien signals. This is called "passive SETI," for "search for extraterrestrial intelligence." If aliens are smart like we are, their technology might send signals into the cosmos. On Earth, for example, all of the radio waves from our phones, satellites and TV station communications "leak" into space, and these leaking radio waves could be picked up if anyone were listening. So Earthlings use telescopes designed to pick up radio waves from space, hoping to find extraterrestrial signals.

That only works for tech-savvy aliens, though. Scientists also use light to look at the kinds of molecules that are present on far-off planets and moons. On Earth, some molecules are usually or always made by living things, so if those molecules are found elsewhere, they could be a sign of life. This kind of research lets scientists look for hints of life on exoplanets that are too far away to reach with a spacecraft.

Scientists also send spacecraft to the nearby places where life might exist. The Mars rovers, for example, collect rock samples that could contain evidence of fossilized ancient Martian microbes. (They haven't found any yet, but you never know!) NASA is planning to send a drone with propellers, called Dragonfly, to Saturn's moon Titan in 2028. Dragonfly would reach Titan by 2034 and search for chemicals tied to life. The European Space Agency would like to send a mission to Enceladus, also to search for signs of past or present life.

NASA's Kepler space telescope before it launched into orbit, trailing Earth around the sun. The telescope is one of the key tools astronomers use to discover exoplanets, or planets outside our solar system.  (Image credit: NASA/KSC)

Are UFOs aliens?

Unidentified flying objects (UFOs) are things in the sky that aren't explained. The first modern UFO sighting goes back to 1947, when a U.S. fighter pilot reported seeing flying saucers in Washington. Not every UFO sighting can be explained, but many turn out to be events with an Earthly origin. For example, the famous "UFO crash" from Roswell, New Mexico, in 1947 was actually debris from an experimental military balloon that was supposed to pick up sound waves from atomic bomb tests in the Soviet Union.

More recently, strange videos have shown seemingly quick-moving, hovering objects. These "unidentified aerial phenomena" (UAPs) don't have an official explanation. However, they could be normal objects that seem to be moving quickly due to optical illusions, or things that aren't what they appear to be. The pilot who took the videos might have been seeing drones, weather balloons or even birds.

Any alien civilization with the kind of technology to build spacecraft has to be an enormous distance away, given that the closest exoplanet that has the right conditions for life is Proxima Centauri B, which is 24 trillion miles away. Proxima Centauri B isn't very close, and it might not have an atmosphere. So it might not have life at all, much less life that could travel to us. And we would need some seriously advanced way to get there: With current Earth technology, it would take 6,300 years for a spacecraft to travel from Earth to Proxima Centauri B.

In other words, no, UFOs probably aren't aliens. An alien civilization could send a spacecraft to our planet, but it would mean the aliens who sent it in the first place — and their kids, grandkids, great-grandkids, great-great-grandkids and so on — would probably be long dead before the craft reached us. So it's a lot more likely that UFO sightings are cases of mistaken identity.

Alien pictures

(Image credit: NASA/JPL-Caltech) The Golden Record When NASA launched the Voyager spacecraft in 1977, they included these Golden Records, which contain images and sounds from Earth. These include greetings in 55 languages, music and pictures of life on Earth. The idea is that if aliens ever encountered them, they would understand what human culture was like.

(Image credit: NASA/JPL-Caltech/MSSS/JHU-APL) Ancient Mars water Landscapes like this one suggest Mars once had a wet surface. Here, a track cut by water in Jezero Crater ends in a fan of sediment that has likely been chemically changed by water.

(Image credit: NASA/JPL/University of Arizona) Jupiter's moon Europa Jupiter's moon Europa might harbor life beneath its icy surface. This moon has a deep ocean beneath a shell of ice, and perhaps hydrothermal vents where life could evolve.

(Image credit: NASA/JPL-Caltech)

Alien world?

This artist's conception shows the exoplanet Kepler-1649c. This planet is similar to Earth in size and temperature and is in its star's habitable zone, the distance where liquid water could exist on the planet's surface.

Discover more about aliens

• What could aliens look like?
• What's the best evidence we've found for alien life?
• Are aliens real?

{ https://www.livescience.com/space }