NASA’s Habitable Worlds Observatory (HWO) will search for biosignatures on Earth-like exoplanets using reflected light spectroscopy.
Eukaryotes originated from the symbiosis of an Asgard archaeon, the alphaproteobacterial ancestor of mitochondria, and possibly additional bacterial contributions.
The habitability of the early Earth was affected by various factors. We focus here on atmospheric oxygen (O2) and methane (CH4). O2 is essential for supporting eukaryotic life, including plants […]
The last eukaryotic common ancestor (LECA) is widely thought to have been an oxygen-respiring organism, arising through endosymbiosis when a free-living bacterium became the mitochondrion.
The tropical oceans that once served as oxygen-rich havens for Earth’s earliest complex life have become the planet’s largest marine dead zones. The dramatic reversal occurred hundreds of millions of […]
The Habitable Worlds Observatory (HWO) is the first NASA Astrophysics flagship mission with a key science goal of searching for signs of life on rocky habitable exoplanets beyond our solar […]
![The multiple roles of methanogens in the modern-day carbon cycle. Processes shown in red contribute to greenhouse gas production. Part of the methane is removed through microbial methane oxidation (A)MO and photochemical reactions, where e is a generic electron donor (e.g., arsenate or sulfate) that is reduced to eH. Processes depicted in green sequester CO2, storing it long-term as carbonates. The size of the arrows relates to the relative biogeochemical importance of the process. The metabolic activity of methanogens may locally alter pH and produce copious amounts of EPS (seen as a veil surrounding the cells in the microphotograph (yellow arrow)). These EPS bind cations (e.g., Ca, Mg) and act as nucleation site, while elevated pH enhances the carbonate precipitation in microbial mats [196]. This contribution by methanogens may ultimately produce microbialites [183] -- preprints.org](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/01/Methanogens-Through-Geological.png?resize=1200%2C720&ssl=1)
Methanogens, also known as methanogenic archaea, are among the most ancient and widespread microorganisms, despite their particular requirements for growth. These oxygen-sensitive microorganisms have impacted climate and biogeochemical cycles throughout […]
Earth was not always the blue-green world we know today: the early Earth’s oxygen levels were about a million times lower than we now experience. There were no forests and […]
However, traditional atmospheric retrieval frameworks are too computationally intensive to explore the high-dimensional parameter spaces such missions will generate.
Searching for signs of life is a primary goal of the Habitable Worlds Observatory (HWO). However, merely detecting oxygen, methane, or other widely discussed biosignatures is insufficient evidence for a […]
