Previous modelling studies have generally concluded that the biogeophysical effects of historical deforestation led to an annual mean cooling in the northern mid-latitudes3,4, in line with the albedo-induced negative radiative forcing from land-cover changes since pre-industrial time reported in the most recent Intergovernmental Panel on Climate Change report⁵. The effects of past land-cover changes on climate are disputed1–3. Phosphine is a promising biosignature gas, as it has no known abiotic false positives on terrestrial planets from any source that could generate the high fluxes required for detection. Yet, because PH3 is spectrally active in the same wavelength regions as other atmospherically important molecules (such as H2O and CH4), searches for PH3 can be carried out at no additional observational cost to searches for other molecular species relevant to characterizing exoplanet habitability.
We calculate that tens of hours of JWST (James Webb Space Telescope) time are required for a potential detection of PH3. Phosphine's weakness as a biosignature gas is its high reactivity, requiring high outgassing rates for detectability. PH3 has three strong spectral features such that in any atmosphere scenario one of the three will be unique compared with other dominant spectroscopic molecules. As with other gases, PH3 can more readily accumulate on low-UV planets, for example, planets orbiting quiet M dwarfs or with a photochemically generated UV shield.
While high, the surface flux values are comparable to the global terrestrial production rate of methane or CH4 (1011 cm-2 s-1) and below the maximum local terrestrial PH3 production rate (1014 cm-2 s-1).
We simulate the atmospheres of habitable terrestrial planets with CO2- and H2-dominated atmospheres and find that PH3 can accumulate to detectable concentrations on planets with surface production fluxes of 1010 to 1014 cm-2 s-1 (corresponding to surface concentrations of 10s of ppb to 100s of ppm), depending on atmospheric composition and ultraviolet (UV) irradiation. On Earth, PH3 is associated with anaerobic ecosystems, and as such, it is a potential biosignature gas in anoxic exoplanets. In this study, we evaluate phosphine (PH3). Beyond the most discussed biosignature gas O2, only a handful of gases have been considered in detail. The corroboration of alien life forms may impact humanity’s understanding of their place in the universe and change people’s attitudes toward global warming and Anthropocene extinction.Ī long-term goal of exoplanet studies is the identification and detection of biosignature gases. The key similarities between UFO sightings and their long and continuous history recorded by witnesses with credentials support the likelihood of alien visitors. Finally, the article considers official reports and statements from the government, military, and scientists to deduce the connection between UAP and alien life. Furthermore, it explores historical accounts of UAP pre-dating the invention of airplanes and hot air balloons. Further, the article outlines examples of pilots who have experienced UAP, along with military reports on “Foo-Fighters” that can be traced back to World War I. Subsequently, it reviews verified cases reported by groups of adults that fulfill specific criteria, such as third-party testimonies, consistent stories, physical evidence, polygraph tests, and follow-up government investigations. First, it examines documented accounts from children witnesses involved in UAP encounters. This article examines multifaceted information and provides a holistic overview to assess the obscurity and controversy behind UAP. However, it is often difficult to believe in the possibility of alien visitors due to the gap between verified UAP sightings and urban legend-like stories of aliens. While the link between Unidentified Aerial Phenomena or Unidentified Flying Objects (UAP or UFOs) and the existence of alien life has long been discredited as pseudoscience, an increasing number of government disclosures and reports on UFOs and their witnesses have recently surfaced that challenge this assertion.