Παρασκευή, 31 Οκτωβρίου 2014

Ένας «LED» ωκεανός στον Τιτάνα. Cassini sees sunny seas on Titan

Ο ωκεανός του Τιτάνα φωτοβολεί καθώς τον χτυπά ο Ήλιος. This near-infrared, color mosaic from NASA's Cassini spacecraft shows the sun glinting off of Titan's north polar seas. While Cassini has captured, separately, views of the polar seas and the sun glinting off of them in the past, this is the first time both have been seen together in the same view. The sunglint, also called a specular reflection, is the bright area near the 11 o'clock position at upper left. This mirror-like reflection, known as the specular point, is in the south of Titan's largest sea, Kraken Mare, just north of an island archipelago separating two separate parts of the sea. This particular sunglint was so bright as to saturate the detector of Cassini's Visual and Infrared Mapping Spectrometer (VIMS) instrument, which captures the view. It is also the sunglint seen with the highest observation elevation so far -- the sun was a full 40 degrees above the horizon as seen from Kraken Mare at this time -- much higher than the 22 degrees seen in PIA18433. Because it was so bright, this glint was visible through the haze at much lower wavelengths than before, down to 1.3 microns. The southern portion of Kraken Mare (the area surrounding the specular feature toward upper left) displays a "bathtub ring" -- a bright margin of evaporate deposits -- which indicates that the sea was larger at some point in the past and has become smaller due to evaporation. The deposits are material left behind after the methane & ethane liquid evaporates, somewhat akin to the saline crust on a salt flat. The highest resolution data from this flyby -- the area seen immediately to the right of the sunglint -- cover the labyrinth of channels that connect Kraken Mare to another large sea, Ligeia Mare. Ligeia Mare itself is partially covered in its northern reaches by a bright, arrow-shaped complex of clouds. The clouds are made of liquid methane droplets, and could be actively refilling the lakes with rainfall. The view was acquired during Cassini's August 21, 2014, flyby of Titan, also referred to as "T104" by the Cassini team. The view contains real color information, although it is not the natural color the human eye would see. Here, red in the image corresponds to 5.0 microns, green to 2.0 microns, and blue to 1.3 microns. These wavelengths correspond to atmospheric windows through which Titan's surface is visible. The unaided human eye would see nothing but haze. Credit: NASA/JPL-Caltech/University of Arizona/University of Idaho

Μια εντυπωσιακή εικόνα έδωσε στη δημοσιότητα η NASA. Πρόκειται για μια σύνθεση από πολλές εικόνες, ένα φωτογραφικό μωσαϊκό όπως το χαρακτηρίζει η NASA, στο οποίο απεικονίζεται η μεγαλύτερη θάλασσα του Τιτάνα να λαμπυρίζει στο Διάστημα. Ο μεγαλύτερος δορυφόρος του Κρόνου βρίσκεται σύμφωνα με τους επιστήμονες σε μια γεωλογική κατάσταση παρόμοια με εκείνη που βρισκόταν η Γη στη βρεφική της ηλικία για αυτό και αποτελεί μόνιμο στόχο παρατήρησης.

Sunglint on a Hydrocarbon Lake: This near-infrared color image shows a specular reflection, or sunglint, off of a hydrocarbon lake named Kivu Lacus on Saturn's moon Titan. Kivu Lacus is a relatively small lake for Titan -- about 48.2 miles (77.5 km) wide -- located very close to the moon's north pole. Image Credit: NASA/JPL-Caltech/University of Arizona/University of Idaho

Στον Τιτάνα υπάρχουν μικρότερες και μεγαλύτερες λίμνες και θάλασσες υγρών υδρογονανθράκων (μεθάνιο, αιθάνιο προπάνιο, βουτάνιο, αιθυλένιο). Η μεγαλύτερη είναι η Θάλασσα Κράκεν (Kraken Mare) που βρίσκεται κοντά στον Νότιο Πόλο του Τιτάνα και στην οποία υπολογίζεται ότι υπάρχουν 45 χιλιάδες χιλιάδες κυβικά χλμ. υγρών υδρογονανθράκων. Σύμφωνα με τους ειδικούς της NASA το λαμπύρισμα προκαλείται από την αντανάκλαση του Ήλιου στη Θάλασσα Κράκεν.

Δεν υπάρχουν σχόλια:

Δημοσίευση σχολίου