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A rocky sphere, with a huge iron core, Mercury


is the closest planet to the Sun. It can sometimes


be glimpsed from Earth near the horizon, in the


east at dawn or in the west at sunset.


WHAT IS THE TEMPERATURE ON MERCURY?
By day, temperatures on Mercury soar as high as
450°C (840°F). This is because Mercury spins round
so slowly on its axis that one place is exposed to the
hot Sun for 88 days at a time. At night, with
little atmosphere, the planet cools rapidly,
and temperatures drop to –180°C (–290°F).

WHAT IS MERCURY’S SURFACE LIKE?
The Mariner 10 and Messenger spacecraft found
Mercury’s surface covered by craters, made mostly
by meteorite impacts billions of years ago. One huge
impact created the Caloris Basin, which is 1,300 km
Diameter (width) at Equator 4,880 km (3,032 miles) (800 miles) wide and ringed by mountain ranges.
Average distance from Sun 57.9 million km (36 million miles)
Time to orbit Sun 88 days
Time to spin around own axis 58.7 days
Mass 0.06 x Earth’s mass
Surface gravity 0.38 x Earth’s gravity
Average surface temperature 167°C (333°F)
Number of moons 0

Diameter (width) at Equator 12,104 km (7,521 miles)
Average distance from Sun 108.2 million km (67.2 million miles)
Time to orbit Sun 224.7 days
Time to spin around own axis 243 days
Mass 0.82 x Earth’s mass
Gravity 0.9 x Earth’s gravity
Average surface temperature 464°C (867°F)
Number of moons 0

HOW HOT IS VENUS?


Temperatures on Venus soar to over 460°C (860°F),


making it hotter than any other planet. Its carbon


dioxide atmosphere, which is 100 times heavier than


Earth’s, traps heat like a greenhouse.


WHY CAN’T WE SEE VENUS’S SURFACE?


Thick clouds in Venus’s atmosphere stop us seeing its


surface. Radar-carrying spacecraft, such as Magellan,


have scanned the surface, showing that it is dotted


with volcanoes and covered with rolling lava plains.


4 MESSENGER
The Messenger spacecraft
was launched in 2004
to go into orbit around
Mercury in 2011 after
making three fly-bys.

4 SCARRED SURFACE
Craters large and small cover
60 per cent of Mercury’s dark
surface. The rocky ground is also
crossed by cracks and ridges, and
smooth plains created by ancient
lava flows.

VENUS


Venus


MERCURY


Mercury


Rocky crust and mantle
cover an iron core that is
3,600 km (2,200 miles) thick


Mercury’s atmosphere is
so thin that it barely exists

MERCURY DATA

Seen from Earth shining brightly in the west at


sunset, Venus is called the evening star. It is a rocky


planet, and the second closest planet to the Sun.


4 TOWERING VOLCANOES
Maat Mons, one of Venus’s many
volcanoes, is about 9 km (5.6 miles)
high. Radar images show that it is
surrounded by lava flows from
repeated eruptions.

Thick sulphuric
acid clouds hide
Venus’s surface

VENUS DATA

Solar panel

Sunshade

Magnetometer

FIND OUT MORE. Earth 16 • Solar System 14 • Volcanoes 44


FIND OUT MORE. Interplanetary Spacecraft 29 • Meteors 23 • Volcanoes 44


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und
mostly

Mercury


Venus

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