NASA Scientist Answers Alien Questions | Tech Support | WIRED

Grinspoon states that while some UFO reports, like the USS Nimitz encounter, are intriguing, there's no scientific reason to link them to extraterrestrial technology. Many sightings can be explained by terrestrial phenomena, camera parallax, or unidentified atmospheric events, rather than alien visitation.

The closest potentially habitable planet is estimated to be around four light-years away, in the Alpha Centauri system. Voyager spacecraft, the fastest human-made objects, would take hundreds of thousands to millions of years to reach a nearby star system.

Water is considered the 'universal solvent' for life due to its ability to dissolve organic molecules and facilitate complex three-dimensional interactions necessary for biological processes. While other liquids exist, water's properties for supporting life are unmatched in experiments.

Assembly theory attempts to differentiate living from non-living matter by quantifying molecular complexity. Life creates highly complex molecules (like amino acids and proteins) that are distinct from the simple molecules prevalent in the rest of the universe, and this complexity serves as a 'techno signature'.

The Drake equation is a framework for estimating the number of communicating civilizations in our galaxy. Its factors include star formation rate, planet formation probability, number of habitable planets, origin of life, evolution of intelligent life, communicating civilizations, and their longevity. While many variables are speculative, the discovery of common planets suggests life should be widespread if its origin isn't exceedingly rare.

The Europa Clipper mission is designed to characterize Europa's habitability, not to directly search for life with a lander yet. This phased approach allows for better target selection for future lander missions, maximizing scientific return and managing mission complexity and cost.

Area 51 is a known testing ground for experimental military aircraft, and there is no scientific evidence to suggest it serves any other purpose related to extraterrestrials.

Named after physicist Enrico Fermi, the paradox questions why, given the vastness and age of the galaxy, there aren't obvious signs of extraterrestrial life. Grinspoon suggests it's not a true paradox because humanity has only searched a tiny fraction of the cosmic 'ocean' for signs of life.

Detecting techno signatures from distant galaxies would require incredibly advanced alien civilizations manipulating their galaxies, perhaps creating Dyson spheres around stars to harvest energy. Such structures would emit unusual infrared signatures, which astronomers can search for.

SETI (Search for Extraterrestrial Intelligence) primarily involves radio and optical (laser pulse) searches. METI (Messages to Extraterrestrial Intelligence) is sending messages, which is more controversial due to concerns about arrogance and the unknown nature of potential recipients.

Scientists look for 'biosignature gases' in exoplanet atmospheres using spectroscopy, which analyzes light at different wavelengths to identify chemical compositions. A recent, unconfirmed report of dimethyl sulfide on exoplanet K2-18b, a gas associated with life on Earth, highlights this method. Water vapor has been confirmed on WASP 96b using this technique.

From an astrobiology standpoint, there are no compelling historical cases of UFOs indicating alien technology. While unusual atmospheric phenomena exist (like sprites), attributing them to aliens is a last-resort explanation, with human technology being a more plausible, though sometimes uncharacterized, alternative.

A 'shadow biosphere' suggests unknown forms of life on Earth that might exist in extreme or unconventional environments not suitable for known life, such as highly acidic zones or deep underground. This concept reminds astrobiologists not to limit their understanding of life's possibilities.

Early Mars had an environment similar to early Earth, with rivers, lakes, and organic molecules, making it highly plausible for life to have originated there. While direct evidence has not yet been found, ongoing rover missions and future sample return missions aim to confirm this.

A Venus sample return mission would be challenging due to its thick, sulfuric acid atmosphere and extreme surface conditions. However, bringing samples back to Earth allows for extensive, prolonged laboratory analysis that surpasses what can be done in situ with remote instruments.

Plate tectonics on Earth plays a crucial role in habitability by recycling nutrients and renewing the surface. While essential for Earth-like life, the absolute necessity of it for all forms of habitability (especially for subsurface ocean worlds like Europa) is still an open question, though some ongoing geological activity is likely required.

With advancements like the James Webb Space Telescope and future instruments, scientists are gaining the ability to identify gases and potentially techno signatures in exoplanet atmospheres. Coupled with increasing sophistication in radio searches, Grinspoon believes there is a decent chance of detecting intelligent life within the next century, assuming it exists to be found.

Ceres, a dwarf planet in the asteroid belt, was found to have a salt deposit in a large crater, indicating past (and possibly present) liquid water. This makes dwarf planets intriguing potential locations for past habitable conditions.

Grinspoon discusses the Trappist-1 system, 40 light-years away, which contains seven planets, three of which are potentially habitable. He highlights the potential for life to spread easily between these closely clustered planets due to meteorite exchange.

Grinspoon believes aliens are real, citing approximately 30 billion habitable planets in our galaxy and no unique magical properties of Earth. While not yet scientifically proven, ongoing research suggests life should be common.

He praises 'Arrival' for its portrayal of alien interaction, particularly the concept of convergent evolution leading to familiar yet distinct alien forms, and the challenges of communication due to fundamentally different cognitions and perceptions of reality.

Exoplanets are discovered indirectly. The 'Doppler shift' method detects a star's wobble caused by a planet's gravitational pull. The 'transit method' observes the slight dimming of starlight as a planet passes in front of its star. The latter, especially with telescopes like Kepler, revealed the abundance of planets in the universe.

Astrobiologists work in universities, government labs, build spacecraft, and conduct field work in extreme environments. Grinspoon shows a stromatolite, a 2.7-billion-year-old rock formed by ancient microbial mats, illustrating early life on Earth.

NASA utilizes Mars rovers for ancient life signs. The Europa Clipper aims to study Europa's vast ocean for habitability in the 2030s. Dragonfly, launching soon, will explore Titan's organic-rich surface with a nuclear-powered drone. The OSIRIS-REx mission returned samples from asteroid Bennu, rich in amino acids and nucleotides, suggesting the ingredients for life are widespread.

The term 'flying saucer' originated from a 1947 pilot's description of objects 'skipping like a saucer,' which was misinterpreted by a newspaper and popularised.

By studying modern organisms, scientists infer characteristics of Luca (the last universal common ancestor) - a single-celled, hot-loving organism from a watery environment. Experiments show that primitive atmospheric gases, sparked with energy, easily form life's building blocks like amino acids, leading to gradual chemical complexity and cell formation.