On
August 27th of this year, Mars will be at its closest distance to Earth in
nearly 60,000 years. The distance between the two planets on this date will be
34.65 million miles (55.76 million kilometers).
The
proximity of the planet can be explained by the elliptical orbits of both Earth
and Mars around the Sun. Earth, being closer to the Sun than Mars, orbits around
the Sun at a higher speed. This makes one Martian year (687 Earth days) nearly
double one Earth year (365 days).
When
both planets are in alignment with the Sun in other words, Earth, Mars and the
Sun are all lined up in a row, and at the same time the furthest point of
Earth’s orbit from the Sun (known as its aphelion) lines up with the closest
point of Mars’ orbit to the Sun (known as its perihelion), the planets will be
at their closest proximity.
The
planet will appear very bright and luminous throughout the month of August
appearing bright red or orange unlike most of the other planets or stars that
have little color. For mid-northern observers, the planet can be seen in the
South sky on any clear night. The best timing to look for the planet is between
midnight and dawn.
Some
of the planet’s features that can be seen using a backyard telescope are the
south polar ice cap, volcanic terrains and maybe even dust storms.
It
is interesting to know that this will not be the nearest the planet will be to
Earth in the near future, in fact the planet is anticipated to be even closer to
Earth in the year 2287 and even closer than that in the year 2729 when the
distance between the two will be approximately 34,580,000 miles (55,651,000
kilometers).
Features
of the Red Planet
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Olympus
Mons is twice as high as Mount Everest
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Mars
has some very interesting and remarkable topography. One of the most impressive
features of the planet is what is known as ‘Olympus Mons’. This huge
inactive volcano rises 78,000 feet (24 km) in the air. That’s twice as high as
Mount Everest. It has a base 500 km in diameter and a 20,000-foot (6 km) high
cliff that borders it.
Tharsis,
a giant bulge rising 10 km from the surface and extending 4000 km across, is
another interesting feature.
The
planet also has a system of canyons known as Valles Marineris. These canyons
that range from 2 to 7 km deep are 4000 km long.
Interestingly,
the southern and northern hemispheres of the planet are quite different. The
southern hemisphere is mainly made up of ancient cratered highlands, such as the
Hellas Planitia, which is an impact crater 2000 km wide and 6 km deep. Whereas
the northern hemisphere is made up of plains, hills, ridges and rift valleys.
Polar
Ice Caps
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The
polar caps
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One
of the planet’s features that may be the easiest to see through your telescope
is the south polar cap as it reflects more sunlight than all other parts of the
planet.
This
ice cap is composed of an inner ‘permanent polar cap’ and an outer
‘seasonal polar cap’. The permanent cap that is made of frozen water is
covered by the seasonal cap that is made of frozen carbon dioxide, also known as
dry ice.
The
outer cap is called the seasonal cap since its presence and bulk depend on the
season. The cap begins to shrink during spring as the Sun shines on it and the
CO2 begins to sublime, meaning it turns back into the gas phase without an
intermediate liquid phase.
The
CO2 in the atmosphere begins to freeze again during winter months forming the
cap. This means that there is less CO2 in the atmosphere and more of it on the
ground. Since the Martian atmosphere is made up of 95% CO2, this phenomenon
causes a drop in atmospheric pressure during winter months and a rise during
summer months. The atmospheric pressure fluctuates as much as 25% between winter
and summer months.
The
higher atmospheric pressure has some important consequences, one of these being
the development of dust storms that can become so huge that they encircle the
entire planet for months.
The
Search for Water on Mars
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Erosions
on the surface of Mars suggest the past existence of river systems or
floods
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Scientists
have long searched for evidence of life on Mars and since, as far as biologists
know, water is essential to life, the search for water has become the main focus
of current scientific missions to Mars.
The
first evidence that the planet may have once harbored liquid water was the
erosion seen in several places that gave the picture of past river systems or
floods. The erosions were dated as being 4 billion years old.
Recent
studies that have led to the discovery of a carbonate known as magnesite, found
almost everywhere on Mars, are likely to rule out the theory that large oceans
or lakes once flowed on the planet’s surface. The discovery of this element
may prove, however, the past or present existence of liquid water on the planet.
The
reason being that carbonates are formed when CO2 reacts with minerals in the
presence of water and although this does not prove for certain that liquid water
existed on Mars, it is good evidence.
The
importance of this finding is that it may support the theory that life may exist
on the planet since even droplets of liquid water could support the existence of
microbial life forms.
On
the other hand, this new evidence would also make the notion of vast bodies of
liquid water far fetched despite the surface features that resemble past sea
floors or lake beds, since more carbonates such as limestone structures would
have been found if such bodies of water had existed.
The
recent discovery of frozen water underneath the surface of almost the entire
planet is believed by scientists to have resulted from the direct interaction
between the atmosphere and dust rather than from oceans.
However
it is still believed by many scientists that the erosions seen on the planet’s
surface must have resulted from some kind of a running liquid, which could have
possibly been carbon dioxide.
NASA
recently launched two robotic rovers, Spirit and Opportunity, on a mission to
Mars. The two rovers, which will arrive at opposite sides of the planet during
the month of January, will be carrying a complete set of cameras and geological
tools that will help them in their mission to discover geological evidence on
the history of water on the planet.
Sources:
*
Aisha
El-Awady has a bachelor’s degree in medicine from Cairo University
and is currently preparing her MA and working as instructor of Parasitology
in the Faculty of Medicine. She may be contacted at: aawady@islam-online.net.
