Sky and Telescope - September 2018 - 15

t PANCAKE DOMES These seven circular hills in Alpha Regio, on average 25 km wide and 750 m high, appear to be thick lava flows that welled
up onto level ground, which allowed them to flow out in an even pattern.

BACKG ROUND: USGS ASTROG EOLOGY SCIENCE CEN TER; CLOUDTOPS: ESA / MPS / DLR / IDA , M. PÉRE ZAY ÚCA R & C. WILSON; PA NCA K E DO MES & TICK: N ASA / JPL; M AG ELL A N TE A M: N ASA / JPL, S&T ARCHIVES

p VENUSIAN TICK This bizarre volcanic construct is a tick, a caldera
surrounded by radiating ridges and valleys. Lava flows breaching the rim
created the "head." Ticks sometimes appear near the deformed terrain
regions called tesserae, but it's unclear if they're related.

Earth, as we know, transformed into a paradise fit for life,
while Venus morphed into a hellscape. It boasts clouds of sulfuric acid and an atmosphere that slams down on the surface
with 90 times the pressure found in Earth's atmosphere. That
surface averages a blistering 460°C (860°F) - hot enough to
melt lead. Smooth, gently rolling plains cover about 70% of
its surface - the result of past volcanic flows, some of which
travel for thousands of kilometers before fanning outward.
Recent research even suggests that volcanism continues
today. Needless to say: Venus is hot, stifling, and dynamic.
Magellan and its predecessors also revealed terrain studded with mountains, plains, high plateaus, canyons, and
ridges. The planet even boasts highlands akin to Earth's
continents. The two largest are the sprawling Aphrodite Terra
along the equator, nearly as large as Europe and Asia combined, and Ishtar Terra in the northern hemisphere, roughly
the size of Antarctica. Those two highlands stand a few kilometers above the plains, roughly similar to the rise of Earth's
continents above its seafloor, and they're marred by more
than 1,000 large volcanoes and 100 mountains - the tallest
of which tower above the landscape at a height greater than
that of Mount Everest in the Himalayas.
But that range of peaks, Maxwell Montes, built up in a different way than the Himalayas, which were created when two
tectonic plates - those large slabs of rock that divide Earth's
crust and jostle about - rammed into each other. In fact,
Venus does not appear to host plate tectonics at all. That much
can be seen from the distribution of volcanoes, which do not

create long chains along the boundaries of tectonic plates like
they do on Earth, but dot the surface haphazardly. It's a mystery whose answer might explain Venus's young landscape, its
stifling atmosphere, and even phenomena on our own world.

Shedding Light on Earth
On Earth, jostling crustal plates help regulate our planet's
temperature over tens to hundreds of millions of years as
carbon dioxide shifts between the atmosphere and Earth's
mantle. So it could be that Venus once had plate tectonics, but over time those plates became thicker and harder to
break apart or subduct. As a result, there was no way to pull
carbon dioxide out of the atmosphere and into the mantle,
forcing the planet down a path that led to extreme temperatures and atmospheric pressures.
u MAGELLAN TEAM
Members of the
Magellan team pore
over images from
the orbiting spacecraft. The map being
studied is assembled
from the long strips of
data from Magellan's
pole-to-pole passes.
From left to right: Nick
Stacy, Ellen Stofan,
Barry Parsons (rear),
and Don Campbell.
sk yandtelescope.com * S E P TE M B E R 2 018

15


http://www.skyandtelescope.com

Table of Contents for the Digital Edition of Sky and Telescope - September 2018

Contents
Sky and Telescope - September 2018 - Cover1
Sky and Telescope - September 2018 - Cover2
Sky and Telescope - September 2018 - 1
Sky and Telescope - September 2018 - Contents
Sky and Telescope - September 2018 - 3
Sky and Telescope - September 2018 - 4
Sky and Telescope - September 2018 - 5
Sky and Telescope - September 2018 - 6
Sky and Telescope - September 2018 - 7
Sky and Telescope - September 2018 - 8
Sky and Telescope - September 2018 - 9
Sky and Telescope - September 2018 - 10
Sky and Telescope - September 2018 - 11
Sky and Telescope - September 2018 - 12
Sky and Telescope - September 2018 - 13
Sky and Telescope - September 2018 - 14
Sky and Telescope - September 2018 - 15
Sky and Telescope - September 2018 - 16
Sky and Telescope - September 2018 - 17
Sky and Telescope - September 2018 - 18
Sky and Telescope - September 2018 - 19
Sky and Telescope - September 2018 - 20
Sky and Telescope - September 2018 - 21
Sky and Telescope - September 2018 - 22
Sky and Telescope - September 2018 - 23
Sky and Telescope - September 2018 - 24
Sky and Telescope - September 2018 - 25
Sky and Telescope - September 2018 - 26
Sky and Telescope - September 2018 - 27
Sky and Telescope - September 2018 - 28
Sky and Telescope - September 2018 - 29
Sky and Telescope - September 2018 - 30
Sky and Telescope - September 2018 - 31
Sky and Telescope - September 2018 - 32
Sky and Telescope - September 2018 - 33
Sky and Telescope - September 2018 - 34
Sky and Telescope - September 2018 - 35
Sky and Telescope - September 2018 - 36
Sky and Telescope - September 2018 - 37
Sky and Telescope - September 2018 - 38
Sky and Telescope - September 2018 - 39
Sky and Telescope - September 2018 - 40
Sky and Telescope - September 2018 - 41
Sky and Telescope - September 2018 - 42
Sky and Telescope - September 2018 - 43
Sky and Telescope - September 2018 - 44
Sky and Telescope - September 2018 - 45
Sky and Telescope - September 2018 - 46
Sky and Telescope - September 2018 - 47
Sky and Telescope - September 2018 - 48
Sky and Telescope - September 2018 - 49
Sky and Telescope - September 2018 - 50
Sky and Telescope - September 2018 - 51
Sky and Telescope - September 2018 - 52
Sky and Telescope - September 2018 - 53
Sky and Telescope - September 2018 - 54
Sky and Telescope - September 2018 - 55
Sky and Telescope - September 2018 - 56
Sky and Telescope - September 2018 - 57
Sky and Telescope - September 2018 - 58
Sky and Telescope - September 2018 - 59
Sky and Telescope - September 2018 - 60
Sky and Telescope - September 2018 - 61
Sky and Telescope - September 2018 - 62
Sky and Telescope - September 2018 - 63
Sky and Telescope - September 2018 - 64
Sky and Telescope - September 2018 - 65
Sky and Telescope - September 2018 - 66
Sky and Telescope - September 2018 - 67
Sky and Telescope - September 2018 - 68
Sky and Telescope - September 2018 - 69
Sky and Telescope - September 2018 - 70
Sky and Telescope - September 2018 - 71
Sky and Telescope - September 2018 - 72
Sky and Telescope - September 2018 - 73
Sky and Telescope - September 2018 - 74
Sky and Telescope - September 2018 - 75
Sky and Telescope - September 2018 - 76
Sky and Telescope - September 2018 - 77
Sky and Telescope - September 2018 - 78
Sky and Telescope - September 2018 - 79
Sky and Telescope - September 2018 - 80
Sky and Telescope - September 2018 - 81
Sky and Telescope - September 2018 - 82
Sky and Telescope - September 2018 - 83
Sky and Telescope - September 2018 - 84
Sky and Telescope - September 2018 - Cover3
Sky and Telescope - September 2018 - Cover4
http://www.nxtbook.com/nxtbooks/newtrack/st_201811
http://www.nxtbook.com/nxtbooks/newtrack/st_201810
http://www.nxtbook.com/nxtbooks/newtrack/st_201809
http://www.nxtbook.com/nxtbooks/newtrack/st_201808
http://www.nxtbook.com/nxtbooks/newtrack/st_201807
http://www.nxtbook.com/nxtbooks/newtrack/st_201806
http://www.nxtbook.com/nxtbooks/newtrack/st_201805
http://www.nxtbook.com/nxtbooks/newtrack/st_201804
http://www.nxtbook.com/nxtbooks/newtrack/st_201803
http://www.nxtbook.com/nxtbooks/newtrack/st_201802
http://www.nxtbook.com/nxtbooks/newtrack/st_201801
http://www.nxtbook.com/nxtbooks/newtrack/st_201712
http://www.nxtbook.com/nxtbooks/newtrack/st_201711
http://www.nxtbook.com/nxtbooks/newtrack/st_201710
http://www.nxtbook.com/nxtbooks/newtrack/st_201709
http://www.nxtbook.com/nxtbooks/newtrack/st_201708
http://www.nxtbook.com/nxtbooks/newtrack/st_201707
http://www.nxtbook.com/nxtbooks/newtrack/st_201706
http://www.nxtbook.com/nxtbooks/newtrack/st_201705
http://www.nxtbook.com/nxtbooks/newtrack/st_201704
http://www.nxtbook.com/nxtbooks/newtrack/st_201703
http://www.nxtbook.com/nxtbooks/newtrack/st_201702
http://www.nxtbook.com/nxtbooks/newtrack/st_201701
http://www.nxtbook.com/nxtbooks/newtrack/st_201612
http://www.nxtbook.com/nxtbooks/newtrack/st_201611
http://www.nxtbook.com/nxtbooks/newtrack/st_201610
http://www.nxtbook.com/nxtbooks/newtrack/st_201609
http://www.nxtbook.com/nxtbooks/newtrack/st_201608
http://www.nxtbook.com/nxtbooks/newtrack/st_201607
http://www.nxtbook.com/nxtbooks/newtrack/st_201606
http://www.nxtbook.com/nxtbooks/newtrack/st_201605
http://www.nxtbook.com/nxtbooks/newtrack/st_201604
http://www.nxtbook.com/nxtbooks/newtrack/st_201603
http://www.nxtbook.com/nxtbooks/newtrack/st_201602
http://www.nxtbook.com/nxtbooks/newtrack/st_201601
http://www.nxtbook.com/nxtbooks/newtrack/st_201512
http://www.nxtbook.com/nxtbooks/newtrack/st_201511
http://www.nxtbook.com/nxtbooks/newtrack/st_201510
http://www.nxtbook.com/nxtbooks/newtrack/st_201509
http://www.nxtbook.com/nxtbooks/newtrack/st_201508
http://www.nxtbook.com/nxtbooks/newtrack/st_201507
http://www.nxtbook.com/nxtbooks/newtrack/st_201506
http://www.nxtbook.com/nxtbooks/newtrack/st_201505
http://www.nxtbook.com/nxtbooks/newtrack/st_201504
http://www.nxtbook.com/nxtbooks/newtrack/st_201503
http://www.nxtbook.com/nxtbooks/newtrack/st_201502
http://www.nxtbook.com/nxtbooks/newtrack/st_201501
http://www.nxtbook.com/nxtbooks/newtrack/st_201412
http://www.nxtbook.com/nxtbooks/newtrack/st_201411
http://www.nxtbook.com/nxtbooks/newtrack/st_201410
http://www.nxtbook.com/nxtbooks/newtrack/st_201409
http://www.nxtbook.com/nxtbooks/newtrack/st_201408
http://www.nxtbook.com/nxtbooks/newtrack/st_mars
http://www.nxtbook.com/nxtbooks/newtrack/st_201407
http://www.nxtbook.com/nxtbooks/newtrack/st_201406
http://www.nxtbook.com/nxtbooks/newtrack/st_201405
http://www.nxtbook.com/nxtbooks/newtrack/st_201404
http://www.nxtbook.com/nxtbooks/newtrack/st_201403
http://www.nxtbook.com/nxtbooks/newtrack/st_201402
http://www.nxtbook.com/nxtbooks/newtrack/st_201401
http://www.nxtbook.com/nxtbooks/newtrack/st_201312
http://www.nxtbook.com/nxtbooks/newtrack/st_201311
http://www.nxtbook.com/nxtbooks/newtrack/st_201310
http://www.nxtbook.com/nxtbooks/newtrack/st_201309
http://www.nxtbook.com/nxtbooks/newtrack/st_201308
http://www.nxtbook.com/nxtbooks/newtrack/st_201307
http://www.nxtbook.com/nxtbooks/newtrack/st_201306
http://www.nxtbook.com/nxtbooks/newtrack/st_201305
http://www.nxtbook.com/nxtbooks/newtrack/st_201304
http://www.nxtbook.com/nxtbooks/newtrack/st_201303
http://www.nxtbook.com/nxtbooks/newtrack/st_201302
http://www.nxtbook.com/nxtbooks/newtrack/st_201301
http://www.nxtbook.com/nxtbooks/newtrack/st_201212
http://www.nxtbook.com/nxtbooks/newtrack/st_201211
http://www.nxtbook.com/nxtbooks/newtrack/st_201210
http://www.nxtbook.com/nxtbooks/newtrack/st_201209
http://www.nxtbook.com/nxtbooks/newtrack/st_201208
http://www.nxtbook.com/nxtbooks/newtrack/st_201207
http://www.nxtbook.com/nxtbooks/newtrack/st_201206
http://www.nxtbook.com/nxtbooks/newtrack/st_201205
http://www.nxtbook.com/nxtbooks/newtrack/st_201204
http://www.nxtbook.com/nxtbooks/newtrack/st_201203
http://www.nxtbook.com/nxtbooks/newtrack/st_201202
http://www.nxtbook.com/nxtbooks/newtrack/st_201201
http://www.nxtbook.com/nxtbooks/newtrack/st_201112
http://www.nxtbook.com/nxtbooks/newtrack/st_201111
http://www.nxtbook.com/nxtbooks/newtrack/st_201110
http://www.nxtbook.com/nxtbooks/newtrack/st_201109
http://www.nxtbook.com/nxtbooks/newtrack/st_201108
http://www.nxtbook.com/nxtbooks/newtrack/st_201107
http://www.nxtbook.com/nxtbooks/newtrack/st_201106
http://www.nxtbook.com/nxtbooks/newtrack/st_201105
http://www.nxtbook.com/nxtbooks/newtrack/st_201104
http://www.nxtbook.com/nxtbooks/newtrack/st_201103
http://www.nxtbook.com/nxtbooks/newtrack/st_201102
http://www.nxtbook.com/nxtbooks/newtrack/st_201101
http://www.nxtbook.com/nxtbooks/newtrack/st_201012
http://www.nxtbook.com/nxtbooks/newtrack/st_201011
http://www.nxtbook.com/nxtbooks/newtrack/st_201010
http://www.nxtbook.com/nxtbooks/newtrack/st_201009
http://www.nxtbook.com/nxtbooks/newtrack/newtrack_st_201009
http://www.nxtbook.com/nxtbooks/newtrack/st_201008_v2
http://www.nxtbook.com/nxtbooks/newtrack/st_201008
http://www.nxtbook.com/nxtbooks/newtrack/st_201007
http://www.nxtbook.com/nxtbooks/newtrack/st_201005_v2
http://www.nxtbook.com/nxtbooks/newtrack/st_201006
http://www.nxtbook.com/nxtbooks/newtrack/st_201005
http://www.nxtbook.com/nxtbooks/newtrack/st_201004
http://www.nxtbook.com/nxtbooks/newtrack/st_201003v4
http://www.nxtbook.com/nxtbooks/newtrack/st_201003v3
http://www.nxtbook.com/nxtbooks/newtrack/st_201003v2
http://www.nxtbook.com/nxtbooks/newtrack/st_201003
http://www.nxtbook.com/nxtbooks/newtrack/st_201002
http://www.nxtbook.com/nxtbooks/newtrack/st_201001
http://www.nxtbookMEDIA.com