Philips Atlas of the Universe

(Marvins-Underground-K-12) #1

THE SOLAR SYSTEM


features which extend over the trailing hemisphere. Other
major craters are Aeneas and Dido. There are also chasma
(Larissa, Tibur) and linea (Carthage, Palatine).
RheaA very ancient, cratered surface. The most prominent
crater is Izanagi, but there are few others of great size,
and they tend to be irregular in shape. As with Dione, the
trailing hemisphere is darkish, with wispy features which
are not unlike those on Dione but are less prominent.
HyperionThis is one of the few medium-sized satellites
which does not have synchronous rotation, and the rotation
period is indeed ‘chaotic’ and variable. Hyperion is less
reflective than the other icy satellites, so there may be a
‘dirty’ layer covering wide areas. There are several craters,
such as Helios, Bahloo and Jarilo, as well as a long ridge
or scarp, Bond-Lassell.
IapetusHere the leading hemisphere is as black as a
blackboard, with an albedo of no more than 0.05, while

the trailing hemisphere is bright: albedo 0.5. The line of
demarcation is not abrupt, and there is a transition zone
200 to 300 kilometres (125 to 190 miles) wide. Some craters
in the bright region (Roncevaux Terra) have dark floors, but
we do not know whether the dark floor material is the same
as the dark area (Cassini Regio). Craters include Otho and
Charlemagne.
Phoebe Whether this should be classed as an icy
satellite is not clear; apparently it has a darkish surface.
Unfortunately it was not closely surveyed by either Voyager.
It may be very similar to the strange asteroid Chiron,
and it is worth noting that in 1664 BCChiron approached
Saturn to within a distance of 16 million kilometres
(10 million miles) which is not much greater than the
distance between Saturn and Phoebe. Like Hyperion,
the rotation period is not synchronous, and amounts to
only 9.4 hours.

SELECTED FEATURES

Lat. ° Long. °
DIONE
Craters
Aeneas 26 N 047
Amata 07 N 287
Adrastus 64 S 040
Dido 22 S 015
Italus 20 S 076
Lausus 38 N 023
Chasmata
Larissa 20–48 N 015–065
Latium 03–45 N 064–075
Palatine 55–73 S 075–230
Tibur 48–80 N 060–080
Linea
Carthage 20–40 N 337–310
Padua 05 N–40 S 245
Palatine 10–55 S 285–320
RHEA
Craters
Izanagi 49 S 298
Izanami 46 S 310
Leza 19 S 304
Melo 51 S 006
Chasmata
Kun Lun 37–50 N 275–300
Pu Chou 10–35 N 085–115
Tapetus
IAPETUS
Craters
Charlemagne 54 N 266
Hamon 10 N 271
Othon 24 N 344
Regio
Cassini 48 S–55 N 210–340
Terra
Roncevaux 30 S–90 N 300–130

180° 150° 120° 90° 60° 30° 0° 330° 300° 270° 240° 210° 180°


-57°


57°


-30°


0° E


30°


S


W


Dione
N

180° 150° 120° 90° 60° 30° 0° 330° 300° 270° 240° 210° 180°


-57°


57°


-30°


0° E


30°


S


W


Rhea
N

180° 150° 120° 90° 60° 30° 0° 330° 300° 270° 240° 210° 180°


-57°


57°


-30°


0° E


30°


S


W


Iapetus
N

D108- 151 UNIVERSE UK 2003CB 7/4/03 5:14 pm Page 119

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