The Daily Omnivore

Ganymede [gan-uh-meed] is a moon of Jupiter and the largest satellite in the Solar System. It has a diameter of 5,268 km (8% larger than Mercury), orbits Jupiter in roughly seven days, and is composed of approximately equal amounts of silicate rock and water ice. A saltwater ocean is believed to exist nearly 200 km below Ganymede’s surface, sandwiched between layers of ice. Ganymede is the only satellite in the Solar System known to possess a magnetosphere, likely created through convection within its liquid iron core. The meager magnetosphere is buried within Jupiter’s much larger magnetic field and connected to it through open field lines. The satellite has a thin oxygen atmosphere that includes O, O2, and possibly O3 (ozone).

Ganymede’s discovery is credited to Galileo Galilei, who was the first to observe it on January 7, 1610. The satellite’s name was soon suggested by astronomer Simon Marius, for the mythological Ganymede, cupbearer of the Greek gods and Zeus’s beloved. A joint NASA/ ESA mission to Jupiter’s icy moons (including Ganymede), the Europa Jupiter System Mission (EJSM), is proposed for a launch in 2020.

Mitochondrial [mahy-tuh-kon-dree-uhl] Eve refers to the most recent common matrilineal ancestor from whom all living humans are descended. Passed down from mother to offspring, all mitochondrial DNA (mtDNA) in every living person is directly descended from hers. Mitochondrial Eve is the female counterpart of Y-chromosomal Adam, the patrilineal most recent common ancestor, although they lived thousands of years apart. Mitochondrial Eve is generally estimated to have lived around 200,000 years ago, most likely in East Africa, when Homo sapiens sapiens were developing as a species separate from other hominids.

One of the misconceptions of mitochondrial Eve is that since all women alive today descended in a direct unbroken female line from her that she was the only woman alive at the time. However nuclear DNA studies indicate that the size of the ancient human population never dropped below some tens of thousands;  there were many other women around at Eve’s time with descendants alive today, but somewhere in all their lines of descent there is at least one man (and men do not pass on their mothers’ mitochondrial DNA to their children). By contrast, Eve’s lines of descent to each person alive today includes at least one line of descent to each person which is purely matrilineal.

Gondwana [gond-wah-nu], originally Gondwanaland, is the name given to a southern precursor supercontinent. Its final geological suturing occurred between ca. 570 and 510 million years ago, joining East Gondwana to West Gondwana. It later separated from Laurasia 180-200 million years ago during the breakup of the Pangaea supercontinent that existed about 500 to 200 million years ago into two large segments, nearly equal in area. The continent of Gondwana was named by Austrian scientist, Eduard Suess, after the Gondwana region of central northern India

The adjective ‘Gondwanan’ is in common use in biogeography when referring to patterns of distribution of living organisms, typically when the organisms are restricted to two or more of the now-discontinuous regions that were once part of Gondwana, including the Antarctic flora. For example, the Proteaceae, a family of plants that is known only from southern South America, South Africa, and Australia are considered to have a “Gondwanan distribution”. This pattern is often considered to indicate an archaic, or relict, lineage.