Unit 16: Astronomy and Space Science, Learning Aim A
The Solar System
Mercury:
It is the closest planet to the sun and the smallest planet; therefore it orbits
the sun faster than the other planets in the solar system. Its name comes
from the swift-footed Roman messenger god. As it is so close to the sun,
the planet’s temperature can reach to an extreme of 140 degree Celsius.
Night temperatures of Mercury can fall to -170 degrees Celsius because the
planet does not have an atmosphere that can trap heat and restore
warmth for the night. Mercury is the smallest planet of our solar system; the planet contains various craters,
including the Caloris Basin, a crater 960 miles- created by an asteroid that hit four billion years ago by an
asteroid from sixty miles away, with a force equivalent to 1 trillion, 1- megaton bombs. Water ice in craters
was discovered in 2012 by NASA’s MESSENGER spacecraft around the north pole of Mercury, where places are
hidden from the sun’s heat. It is thought that the southern pole of Mercury may also contain them; however
MESSENGER’s orbit hasn’t allowed the discovery to take place. Mercury is continuously shrinking in size, like it
has been in the past because of the continental plate which is over an iron core which as it cools, it solidifies:
this reduces the volume of the planet. It is the second densest planet, the first being the Earth; its metallic core
is approximately 2,200- 2,400 miles, whereas its outer shell is 300-400 thick. Mercury also possesses a
magnetic field which was discovered by Mariner 10 (Space.com 2017).
Venus:
The planet is named after Aphrodite, ancient Roman goddesses of love and
beauty. Venus is similar in size to Earth, with a radius of 3,760 miles. Venus is six
sunlight- minutes away from the sun, in other words, 0.7 astronomical units.
Unlike many other planets, Venus rotates from east to west direction, like
Uranus. Both of these planets complete the longest rotation compared to the
other planets, with one rotation being in 243 Earth days. Venus makes a circular
orbit around the sun in 255 Earth days, with a three degree tilt, which affects it
in a way that it doesn’t have prominent seasons such as winter or autumn. Venus’ formation started with
swirling gas and dust together due to the force of gravity. Venus’ construction consists of a central core, a
rocky mantle and a solid crust. Venus is the hottest planet in our solar system as it includes a strong
atmosphere of greenhouse gases and where clouds are made of carbon dioxide and sulphuric acid. Its
atmosphere can trap immense heat, which could turn metals into liquid due to the planet’s heat intensity
Venus unfortunately doesn’t contain any rings or doesn’t have any moons to orbit around. Venus’ surface
temperature is about 900 degrees; scientists believe that there was once water that existed on Venus and
explorers are ongoing in search for maybe an ancient ocean (NASA 2019).
Earth:
Earth is a terrestrial planet that is the biggest of the four, rock and metal, planets
closest to the sun. Unlike the other planets that are named after Greek and Roman
gods, Earth is the definition of the ground, in German. Earth’s composition is made
up of rocky material, with a surface filled with natural composites such as mountains
and canyons. The Earth’s lithosphere includes a continental and oceanic crust and a
upper mantle, which is always moving. The atmosphere is the perfect place for life, as
, we know, with the atmosphere being 78% of nitrogen, 21% oxygen and 1% of other gas. The Earth has a radius
of 3,959 miles and is the biggest of the terrestrial planets. The Earth is one astronomical unit away from our
Sun (the unit is used for a easier comparison of the planets’ distances away from the Sun). The Earth has only
one moon, which stabilises the Earth’s wobble- this, has made the climate less variable over thousands of
years. The moon is the fifth largest moon in the solar system and is approximately 238,855 miles away from
the Earth. Unfortunately like Mercury and Venus, Earth does not have a ring. With
a 23.5 degree tilt, Earth is responsible for our cycle of seasons in a year. The Earth
completes one rotation in 23.9 hours and takes 365 and a quarter days to
complete an orbit around the sun; this is where our leap year after every four
years is used (NASA Science 2019)
Mars:
Mars, also known as the red planet, consists of a chilling, desert atmosphere that
has a thin atmosphere. Its length of year is a measurement equivalent to 687
Earth days and has showed an evidence of activity in the past as well as knows,
and it includes ice caps and canyons, as well as now extinct volcanoes, similar to
the Earth. It is thought that there may, or may have been extraterrestrial life on
the red planet due to evidence found of a thick, wetter and warmer atmosphere found by spacecrafts. Mars is
at an average distance of 142 million miles away from the Sun, which in astronomical units is 1; it takes 13
minutes for sunlight to travel to the red planet. Mars’ axis rotation is similar to Earth where it is 25 degrees
and the Earth has a 24.3 degree tilt. Mars also has prominent seasons, but they are longer and vary in length
because of its elliptical orbit around the Sun. Mars formed as gravity pulled gas and dust into a planet, like the
other terrestrial planets, it has: a core, a rocky mantle and a solid crust. The core is between 930 and 1,300
miles deep, made of mainly iron. A rocky mantle of 770-1,170 miles thick surrounds it (made of metals such as
magnesium and potassium) and lastly the crust tops it off with being only 6-30 miles deep. The background
behind Mars being called the ‘red planet’ is mainly due to the oxidation of iron in the rocks, commonly
referred as ‘Martian soil’ .The planet appears red from space due to the dust being kicked into its atmosphere
due to winds, which can occur dust storms. Temperatures in Mars can reach as high as 20 degrees Celsius, or
fall down to -153 degrees Celsius. Mars has two small moons which are named as Phobos and Deimos: they
are both shaped like potatoes as they weigh too small for gravity to alter their shape into more moon-like.
Phobos is the larger moon out of the two and is predicted to crash into Mars in maybe 50 million years.
Deimos is only half the size of the other moon and is filled with loose dirt on its craters; this moon orbits two
and a half times further away from Mars. Mars doesn’t have any rings; if Phobos crashes, it is thought that it
could create a dusty ring (NASA Science- Solar System Exploration 2019).
Jupiter:
Jupiter is a planet that is twice as big if you combine all the other planets in our
solar system; it is approximately 488,825,020 miles away from the sun and it
takes 43,735135 minutes precisely or light to get from the sun to Jupiter. The
features found on Jupiter: its stripes and swirls are windy clouds that are
ammonia and water; floating in an atmosphere of hydrogen and helium. Jupiter
orbits 5.2 astronomical units from our sun, or it can also be measured as 284
million miles. Jupiter’s rotation cycle involves it rotating only one every 10 hours,
also known as a Jovian day, but it takes 12 Earth years to complete an orbit of the
Sun. Jupiter’s atmosphere is only mainly made u of two elements, which are
hydrogen and helium; similar to the sun. Jupiter has the largest ocean in the
ocean because of all the pressure and temperature increase, which causes the
gaseous atmosphere to turn to liquid. Jupiter has a lot more moons compared to the other planets that only
have a few and moreover, some do not possess any: Jupiter has more than 75 moons. In 1975, the Voyager
mission founded Jupiter’s faint ring system. As far as we know, only some of Jupiter’s moons contain oceans
