TheUnited Launch Alliance's (ULA) reusable XEUS vehicle would use ACES cryotanks capable of storing up to 68 tonnes of LOX/LH2 propellant. Filling up with liquid hydrogen and oxygen at a LOX/LH2 propellant producing water depot located at EML1, the XEUS could be used to transports astronauts, round trip, between EML1 and the surface of the Moon.
The XEUS could also be used to transport astronauts between propellant depots located at LEO and EML1 or EML2.
Beyond cis-lunar space, the XEUS vehicle could be used to access the
surfaces of Mercury, asteroids in the asteroid belt such as Ceres,
Vesta, and Psyche, Jupiter's moon, Callisto, and also the moons of
Mars, Phobos and Deimos.
As a cargo transport
operating out of EML1, the XEUS could deliver more than 50 tonnes of
cargo to the lunar surface or transport more than 50 tonnes of water
extracted from the lunar ice back to propellant producing water depots
located at EML1 or EML2.
Deployed into Earth orbit by a Vulcan/ACES 68 launch vehicle in the early 2020s, the XEUS could give NASA, the DOD, other government space agencies, and even space tourist easy access to the surface of the Moon and back while helping to give humans access to other regions of the solar system.
Skull of Oreopithecus (Credit: After Szalay and Berzi, 1973)
Primates, of course, are generally characterized by their grasping hands and feet. While the toes of human feet have lost their prehensile capability, the fingers of human hands have the most sophisticated manipulative ability of any primate. Humans are the only hominoid (humans and apes) primate capable of supplying the substantial force necessary for holding objects steadily and securely between the pads of the thumb and one or more fingers. This is called a pad-to-pad precision grip.
Fossil evidence suggest that early hominins (humans and their ancestors) such as Australopithecus also possessed a pad-to-pad precision grip.
In 1970, Clifford Jolly suggested that human manipulative capability may have paralleled those of the small object feeding gelada baboon (Theropithecus), a largely terrestrial East African primate that uses its pad-to-pad precision grip to feed on grasses and the seeds of grasses. Jolly suggested that such a folivorous diet in early hominin ancestors might also explain the reduction in hominin canine size.
But in 1977, marine biologist, Alister Hardy proposed an alternative hypothesis for the origin of the human pad-to-pad precision grip. He hypothesized that the hominin precision grip was originally an adaptation for the intensive exploitation of benthic invertebrates while wading bipedally in shallow water. In 1960, Alister Hardy suggested that the sensitive probing fingers
of humans may have evolved in human ancestors adapted for the
exploitation of shelfish and other benthic organisms. Hardy also proposed that bipedal wading for benthic organism was the selective reason for the evolution of obligatory bipedalism in the earliest hominins.
In 1999, Salvador Moyà-Solà, Meike Köhler, and Lorenzo Rook presented evidence for the possession of a pad-to-pad precision grip in the 7.6 million fossil hominoid, Oreopithecus bambolii.
Oreopithecus has been vernacularly called the 'Swamp Ape' because of its apparent preference for swampy wetland environments. This late Miocene hominoid was also the earliest bipedal ape and lived in isolation from the European and African continents on an ancient Mediterranean island known as Tuscany-Sardinia. Rather abundant oreopithecine fossils have been found in lignite layers along with the fossil remains of freshwater mollusk, turtles, otters, and crocodiles (the possible predators involved in the deaths of the oreopithecine remains).
Paleontologist such as Birdsell, Harrison, and Rook have suggested that Oreopithecus may have exploited these aquatic plants as a food resource. And sedges, water lilies, reeds, cattail, pond- weeds, horestails, and
stoneworts, and other wetland plants which were also abundantly represented
in the fossil pollen spectrum.
Feeding on aquatic vegetation is certainly not unusual in modern primates and has been observed in lemurs, chimpanzees, gorillas, baboons, the Colobus monkeys and, of course, in humans. Groups of Colobus monkeys have been known to descended from trees and to travel to pools of open water in swampy areas in order to feed on aquatic vegetation. Western Gorillas are also known to wade bipedally into swamps to feed on aquatic plants, sometimes even using walking sticks to stay erect.
Human pad-to-pad precision grip (Credit: Alister Hardy, 1977)
The short legs of Oreopithecus along with its peculiar feet which exhibit a widely abducted hallux suggest that the swamp apes were less adapted for terrestrial locomotion than in the early African hominins. The short hindlimbs and the pedal tripod formed by widely abducted hallux and the deviated metatarsals of Oreopithecus appear to be designed as a stable platform for efficient postural harvesting which would have been advantageous for wading for food items in shallow aquatic environments.
While the cranio-dental evidence strongly indicates that Oreopithecus was intensely herbivorous, the unusual amount of wear on the canines and incisors in addition to the thickness of the central incisors which bear a number of small mammelons, may suggest that aquatic vertebrates were also included in their diets. As earlier noted, freshwater mollusks were abundant in the ancient wetland environments that Oreopithecus frequented. Oreopithecus also possessed a hominin-like pad-to-pad precision grip which they could have utilized to apprehend aquatic invertebrates while using their fingers, canines and central incisors to pry open and scrape out the edible flesh of the hard shelled freshwater bivalves.
Sometime after 7.4 million years ago, sea levels began to fall in the Mediterranean creating land bridges to North Africa. Global sea levels fell to such an extent that eventually the Mediterranean Sea
became completely isolated from in the inflow of marine waters from the
Atlantic Ocean 6.1 million years ago.
The earliest African hominin, Sahelanthropus, appeared in the fossil record in North Africa sometime between 6.8 and 7.2 million years ago. While not much is known about the postcranial remains of Sahelanthropus, its craniodental morphology isremarkably similarto that of Oreopithecus bambolii.
Aquatic foraging in the wetland swamps of Tuscany-Sardinia would, therefore, explain the adaptive value of bipedal behavior, pad-to-pad precision grips and intense folivory in Oreopithecus and the origins of obligatory bipedalism, precision grips, and hyper-mastication in hominin evolution. And this would appear to be further evidence that Oreopithecus was the earliest bipedal human ancestor.
"The knowledge that we have now is but a fraction of the knowledge we must get, whether for peaceful use or for national defense. We must depend on intensive research to acquire the further knowledge we need ... These are truths that every scientist knows. They are truths that the American people need to understand." (Harry S. Truman 1948).