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TitleAtlas of the Universe Part01
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Table of Contents
                            Atlas of the Universe
Contents
Foreword
Introduction
Exploring the Universe
	Astronomy through the Ages
	Telescopes and the Stars
	Observatories of the World
	Great Telescopes
	Invisible Astronomy
	Rockets into Space
	Satellites and Space Probes
	Man in Space
	Space Stations
	The Hubble Space Telescope
The Solar System
	The Sun's Family
	The Earth in the Solar System
	The Earth as a Planet
	The Earth's Atmosphere and Magnetosphere
	The Earth–Moon System
	Features of the Moon
	Lunar Landscapes
	The Far Side of the Moon
	Missions to the Moon
	Clementine and Prospector
	The Moon: First Quadrant (North-East)
	The Moon: Second Quadrant (North-West)
	The Moon: Third Quadrant (South-West)
	The Moon: Fourth Quadrant (South-East)
	Movements of the Planets
	Mercury
	Features of Mercury
	Map of Mercury
	Venus
	Mapping Venus
	The Magellan Mission
	Mars
	Missions to Mars
	Satellites of Mars
	Map of Mars
	Hubble Views of Mars
	Mars from Global Surveyor
	The Search for Life on Mars
	The Pathfinder Mission
	Asteroids
	Exceptional Asteroids
	Jupiter
	The Changing Face of Jupiter
	Missions to Jupiter
	Impacts on Jupiter
	Satellites of Jupiter
	The Galilean Satellites – from Galileo
	Maps of Jupiter's Satellites
	Saturn
	Rings of Saturn
	Details of Saturn's Rings
	Missions to Saturn
	Satellites of Saturn
	Maps of Saturn's Icy Satellites
	Titan
	Uranus
	Missions to Uranus
	Satellites of Uranus
	Maps of the Satellites of Uranus
	Neptune
	Satellites of Neptune
	Pluto
	The Surface of Pluto
	Boundaries of the Solar System
	Comets
	Short-Period Comets
	Halley's Comet
	Great Comets
	Millennium Comets
                        
Document Text Contents
Page 1

‘The best introduction to astronomy’
The Journal of the British Astronomical Association

‘The best introduction to astronomy’
The Journal of the British Astronomical Association

ATLAS OF THE
UNIVERSE

SIR PATRICK MOORESIR PATRICK MOORE
R E V I S E D E D I T I O NR E V I S E D E D I T I O N

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Page 72

M a p p i n g Ve n u s

72

A T L A S O F T H E U N I V E R S E

Because we can never see the surface of Venus, the onlyway to map it is by radar. It has been found that Venus
is a world of plains, highlands and lowlands; a huge
rolling plain covers 65 per cent of the surface, with low-
lands accounting for 27 per cent and highlands for only
8 per cent. The higher regions tend to be rougher than the
lowlands, and this means that in radar they are brighter (in
a radar image, brightness means roughness).

There are two main upland areas, Ishtar Terra and
Aphrodite Terra. Ishtar, in the northern hemisphere, is
2900 kilometres (1800 miles) in diameter; the western
part, Lakshmi Planum, is a high, smooth, lava-covered
plateau. At its eastern end are the Maxwell Mountains,
the highest peaks on Venus, which rise to 11 kilometres
(nearly 7 miles) above the mean radius and 8.2 kilometres
(5 miles) above the adjoining plateau. Aphrodite straddles
the equator; it measures 9700 � 3200 kilometres (6000 �
2000 miles), and is made up of several volcanic massifs,
separated by fractures. Diana Chasma, the deepest point
on Venus, adjoins Aphrodite.

(En passant, it has been decreed that all names of fea-
tures in Venus must be female. The only exception is that
of the Maxwell Mountains. The Scottish mathematician
James Clerk Maxwell had been placed on Venus before
the official edict was passed!)

A smaller highland area, Beta Regio, includes the
shield volcano, Rhea Mons and the rifted mountain Theia
Mons. Beta, which is cut by a huge rift valley rather like
the Earth’s East African Rift, is of great interest. It is
likely that Rhea is still active, and there can be no doubt
that the whole surface of Venus is dominated by vul-
canism. Venus’ thick crust will not slide over the mantle
in the same way as that of the Earth, so that plate tectonics
do no apply; when a volcano forms over a hot spot it will
remain there for a very long period. Lava flows are found
over the whole of the surface.

Craters are plentiful, some of them irregular in shape
while others are basically circular. The largest, Mead, has a
diameter of 280 kilometres (175 miles), though small craters
are less common than on Mercury, Mars or the Moon.

There are circular lowland areas, such as Atalanta
Planitia, east of Ishtar; there are systems of faults, and
there are regions now called tesserae – high, rugged tracts
extending for thousands of square kilometres and charac-
terized by intersecting ridges and grooves. Tesserae used
to be called ‘parquet terrain’, but although the term was
graphic it was abandoned as being insufficiently scientific.

Venus has been contacted by fly-by probes, radar-
carrying orbiters and soft-landers; in 1985 the two Russian
probes en route for Halley’s Comet even dispatched two
balloons into the upper atmosphere of the planet, so that
information could be sent back from various levels as the
balloons drifted around. The latest probe, Magellan, has
confirmed and extended the earlier findings that Venus is
overwhelmingly hostile.

▲ Topographic globes

of Venus. Pioneer Venus 2
visited Venus in 1978. The
mission involved an entry
probe and a ‘bus’ which
dispatched several small
landers which sent back
data during their descent.
The map was compiled as
a false-colour representation
with blue indicating low
levels and yellow and
red higher areas. Ishtar
and Aphrodite stand out
very clearly. It has been
suggested that in the future
it may be possible to ‘seed’
the atmosphere, breaking
up the carbon dioxide and
sulphuric acid and releasing
free oxygen.

�� The topography of
Venus, in perspective views
generated by computer
using Magellan data. They
are, of course, false colour.
The image immediately

below shows lowland plain
in Sedna Planitia. The other
two images show the
typically Venusian highland
terrain of Ovda Regio,
bordered by plains.

C Atl of Univ Phil'03stp 2/4/03 2:58 pm Page 72

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� � The topography of
Venus. These images were
obtained by the Magellan
radar altimeter during its
24 months of systematic
mapping of the surface of
Venus. Colour is used to
code elevation, and
simulated shading to
emphasize relief. Red
corresponds to the highest,
blue to the lowest elevations.
At left are the two polar
regions in orthographic
projection. The image at far
left is centred on the North
Pole, and that at near left on
the South Pole. The four
images at right are
hemispheric views centred
on (from top to bottom)
0 degrees east, 90 degrees
east, 180 degrees east and
270 degrees east longitude.
North is at the top. The
resolution of detail on the
surface is about 3 km
(2 miles). A mosaic of the
Magellan images forms the
base for the maps; gaps in
the coverage were filled with
images from the Earth-based
Arecibo radar, with extra
elevation data from the
Venera spacecraft and the
US Pioneer Venus missions.

73

T H E S O L A R S Y S T E M

Feature Lat.° Long.°

T E R R A E Aphrodite 40 S–5 N 140–000
Ishtar 52–75 N 080–305

R E G I O N E S Alpha 29–32 S 000
Asteria 18–30 N 228–270
Beta 20–38 N 292–272
Metis 72 N 245–255
Phoebe 10–20 N 275–300
Tellus 35 N 080
Thetis 02–15 S 118–140

P L A N I T I A Atalanta 54 N 162
Lakshmi Planum 60 N 330
Lavinia 45 S 350
Leda 45 N 065
Niobe 138 N–10 S 132–185
Sedna 40 N 335

C H A S M A Artemis 30–42 S 121–145
Devana 00 289
Diana 15 S 150
Heng-O 00–10 N 350–000
Juno 32 S 102–120

C R A T E R S Colette 65 N 322
Lise Meitner 55 S 322
Pavlova 14 N 040
Sacajewa 63 N 335
Sappho 13 N 027

V O L C A N O Rhea Mons 31 N 285
M O U N T A I N Theia Mons 29 N 285

F E A T U R E S O N V E N U S – S E L E C T E D L I S T

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Page 143

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T H E S O L A R S Y S T E M

It also was visible at the same time as the Sun, and it had a
long, imposing tail. The orbit is elliptical, but we will not
be seeing the comet again yet awhile, because the estimated
period is of the order of 4 million years. Obviously we
cannot be precise; we can measure only a very small seg-
ment of the orbit, and it is very difficult to distinguish
between a very eccentric ellipse and a parabola.

Comet Skjellerup–Maristany of 1927 was also very
brilliant, but its glory was brief, and it remained incon-
veniently close to the Sun in the sky. This was also true,
though not to so great an extent, of Comet 1965 VIII, dis-
covered independently by two Japanese observers, Ikeya
and Seki. From some parts of the world it was brilliant for
a while, but it soon faded, and will not be back for at least
880 years. Kohoutek’s Comet of 1973 was a great dis-
appointment. It was discovered on 7 March by Lubos
Kohoutek at the Hamburg Observatory, and was expected
to become extremely brilliant, but it signally failed to do
so, and was none too conspicuous as seen with the naked
eye. Perhaps it will make a better showing at its next
return, about 75,000 years from now.

Of lesser comets, special mention should be made of
Arend–Roland (1957), Bennett (1970) and West (1976).
Arend–Roland was quite conspicuous in the evening sky
for a week or two in April 1957, and showed a curious
sunward spike which was not a reverse tail, but was due
merely to thinly spread material in the comet’s orbit
catching the sunlight at a favourable angle. Bennett’s
Comet was rather brighter, with a long tail; the period here

Year Name Date of Greatest Mag. Min. dist. from
discovery brightness Earth, 106 km

1577 1 Nov 10 Nov �4 94
1618 16 Nov 6 Dec �4 54
1665 27 Mar 20 Apr �4 85
1743 De Chéseaux 29 Nov 20 Feb 1744 �7 125
1811 Flaugergues 25 Mar 20 Oct 0 180
1843 5 Feb 3 Jul �7 125
1858 Donati 2 June 7 Oct �1 80
1861 Tebbutt 13 May 27 June 0 20
1874 Coggia 17 Apr 13 July 0 44
1882 Great Southern Comet 18 Mar 9 Sept �10 148
1910 Daylight Comet 13 Jan 30 Jan �4 130
1927 Skjellerup–Maristany 27 Nov 6 Dec �6 110
1965 Ikeya–Seki 18 Sept 14 Oct �10 135
1996 Hyakutake 30 Jan 1 May �1 21
1997 Hale–Bopp 22 July 1995 30 Apr �1.5 193

S E L E C T E D L I S T O F G R E A T C O M E T S

is about 1700 years. West’s Comet was also bright, but
suffered badly as it passed through perihelion, and the
nucleus was broken up. No doubt observers will be inter-
ested to see what has happened to it when it returns in
around the year AD 559,000.

The only really bright comets of very recent years
came in 1996 and 1997 – Comet Hyakutake and Comet
Hale–Bopp. When the next will appear we do not know,
but we hope it will not be too long delayed. At least
the appearance of two bright comets so near the end of the
20th century is encouraging.

▲ The Great Comet of 1843,

as seen from the Cape of
Good Hope on the evening

of 3 March. This may have
been the brightest comet
for many centuries.

▲ De Chéseaux’s Comet of

1744, with its multiple tail;
this is a famous impression
of it, but it did not remain
brilliant for long, and is not
well documented.

▼ Donati’s Comet of 1858,

often said to have been
the most beautiful comet
ever seen; it had tails of
both types.

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Page 144

M i l l e n n i u m C o m e t s
The closing years of the old century were graced by twobright comets. The first of these was discovered on 30
January 1996 by the Japanese amateur Yuji Hyakutake,
using 25 � 150 binoculars; it was then of the 11th mag-
nitude. It brightened steadily, and moved north in the
sky; it reached perihelion on 1 May 1996, at 34 million
kilometres (21 million miles) from the Sun. On 24 March
it had passed Earth at 15 million kilometres (9,300,000
miles) – 40 times as far away as the Moon. At this time
it was near Polaris in the sky; the magnitude was �1,
and there was a long, gossamer-like tail extending for
100 degrees. The main feature of the comet was its beauti-
ful green colour. It faded quickly during April; its period
is around 15,000 years. In fact it was a small comet, with
a nucleus estimated to be no more than 3.2 kilometres
(2 miles) in diameter.

The second bright comet was discovered on 22 July
1995 independently by two American observers, Alan

144

A T L A S O F T H E U N I V E R S E

▲ Comet Hyakutake,

photographed in 1996 by
Akira Fujii. Note the
lovely green colour of the
comet in this photograph.

� Comet Hale–Bopp,

photographed by Akira Fujii
on 10 March 1997. Note the
clear separation of the long
blue ion tail and the dust tail.

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