Enceladus Flyby

The North Pole of Enceladus during the October 30th, 2015 Cassini Flyby (NASA/ESA/ASI)

Since 2004, the Cassini spacecraft has been in orbit around Saturn. The robot probe (a joint effort of NASA, ESA, and the Italian space agency) received the most press when it launched a flying saucer lander onto Saturn’s planet-like moon Titan, but it is still out there doing amazing work. Last week, while I was busy writing about Halloween themes, the probe made its closest pass yet to Saturn’s ice moon, Enceladus. Enceladus is only 500 kilometers in diameter and it is coated in ice, but it is of great interest to scientists because ice plumes venting from the moon’s south pole seem to indicate a large polar subsurface ocean of liquid water. Warmed above freezing by tidal flux, this ocean beneath the ice probably has a thickness of around 10 km.

View of Enceladus’ south pole geyser, backlit by Saturn

On October 30th, Cassini flew by the icy moon at the dangerously close distance of 30 kilometers (18.6 miles). The probe was directly above the south pole of Enceladus and it collected a little flake of ice to analyze (which strikes me as incredibly amazing and beautiful). It will take some time for the ship’s devices to assay the drop of water from an alien ocean, but Cassini also snapped some photos which we already have. These are taken from point blank range above the south pole. The ocean is down there beneath the scratches and scars. What is the nature of this icy ocean? How long has it been there? Could it possibly harbor life?

Treeshrews (Banxrings)

Common Tree Shrew (Tupaia glis)

According to contemporary taxonomy, the primates (whom I haven’t yet written about because they are so near and dear) are closely related to two other groups of living mammals—both of which are native to Southeast Asia.  The closest family, the Colugos, consist of two species of delicate tree-gliding mammals described here.   The other close relatives are treeshrews (aka banxrings), 20 species of (largely) arborial tree-shrews which make up an entire order, Scandentia.

A Northern Tree Shrew (Tupaia belangeri)

Actually “treeshrew” is a misnomer, the banxrings are not true shrews at all.  They are small slight animals with long tails and neutral colored fur.  They have large sophisticated eyes and they are largely diurnal.  The arborial species have binocular vision so they can navigate in a three-dimensional world of branches where leaps must be perfectly gauged.  The slightly larger terrestrial species uses its claws to dig for insects, grubs, and roots.  All banxrings are omnivorous, feeding on arthropods, tiny vertebrates, seeds, berries, and fruits.

The pen-tailed tree-shrew (Ptilocercus lowii)

Treeshrews live in jungles, forests, mixed woodlands and bamboo groves.  They range from India to Vietnam down through Southern China, Malaysia, and Indonesia.  Of all mammals they have the largest brain to body mass ratio (although considering their slight mass that isn’t saying too much).   They are social and families mark out small territories which they mark and vigorously defend.   The treeshrews are anxious skittish creatures since they have numerous predators, including birds of prey, small carnivores, and snakes.

Treeshrew mothers leave their helpless silent babies for up to two days at a time.  When the mother returns the baby treeshrews can put on up to 60% of their weight in one feeding.  The mother is not inattentive: she interacts infrequently with her offspring so that they are not discovered by predators while they are completely helpless.  Once the treeshrews grow big enough to venture beyond the nest, the mother becomes extremely engaged with them and she helps them to learn about predators, gathering food, and climbing.