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General: NEW YEAR ON MARS NOVEMBER 12TH 2024 BACK TO THE FUTURE WHY?
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by European Space Agency
 To mark 20 years of ESA’s Mars Express, the High Resolution Stereo Camera (HRSC) team has produced a new global colour mosaic: Mars as never seen before. The mosaic reveals the planet’s surface colour and composition in spectacular detail. Credit: ESA/DLR/FU Berlin/G. Michael 12 November 2024 marks the start of a new year on Mars. At exactly 10:32 CET/09:32 UTC on Earth, the Red Planet begins a new orbit around our sun.
This is the 38th Martian year. The convention for counting years in the Martian calendar started in 1955, with the first year coinciding with a major storm named "the great dust storm of 1956."
There are some significant differences between years on the two planets:
- Days: A Martian day is called a "sol" and lasts 24 hours and 39 minutes, slightly longer than an Earth day.
- Years: One year on Mars equals 687 Earth days, or 668 sols, nearly twice as long as an Earth year. If you would like to know your Martian age, divide your current age by 1.88 and tell your friends how much younger you are… on Mars, at least!
- New Year: The Martian New Year begins on the northern equinox (northern spring, southern autumn on Mars).
- Seasons: Like Earth, Mars has four seasons—winter, spring, summer and autumn. Unlike Earth's seasons, Martian seasons are not of equal lengths due to Mars' more elliptical orbit. The planet's axial tilt causes the northern hemisphere to receive more sunlight during the northern summer, and the southern hemisphere to receive more sunlight in northern winter. Winter and summer come when the northern and southern hemispheres tilt away from the sun in turn.
- Dust seasons: The second half of the Martian year is often marked by fierce dust storms that can sometimes become planet-wide. As Mars swings closer to the sun, the atmosphere heats up, causing winds to lift up very fine particles from the Martian soil. Once airborne, these brownish particles heat up and redistribute some of that warmth to the surrounding atmosphere. This process can rapidly pump a lot of dust.
- Weather: Temperature swings between day and night are extreme on Mars. At noon on a summer's day, air temperature can reach 0ºC but will plunge to -60ºC at night. In winter, night temperatures are even colder, dropping to -110ºC. A recurring weather phenomenon is the Arsia Mons Elongated Cloud, a cloud of ice crystals that can reach up to 1800 kilometers in length.
 Credit: European Space Agency
https://phys.org/news/2024-11-happy-year-mars.html
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Science: Encounter with Saturn confirms relativity theory
By Marcus Chown
WHEN THE spaceprobe Voyager 1 flew past Saturn in 1980, it not only
observed the planet and its moons but also provided scientists with data
that confirms Einstein’s general theory of relativity. In 1915, Einstein
predicted that light loses energy climbing out of the ‘gravitational well’
of a massive body, such as a planet. The effect is known as the gravitational
red shift, because as light loses energy its frequency is reduced, making
it appear redder.
Voyager 1 was able to test the red shift effect when it flew past Saturn,
using radio signals sent back to Earth by a transmitter locked at a very
precise frequency. The spaceprobe was equipped with an ultrastable crystal
oscillator, known as the USO. This acted as a very precise standard, varying
its frequency by less than 5 parts in 1012. Electronic equipment on board
multiplied the frequency of the oscillator by 120 times, to provide the
frequency of the spaceprobe’s radio transmitter – 2.3 gigahertz. These signals
were then picked up by the radio telescopes of NASA’s Deep Space Network,
which was used to track and control both Voyager spaceprobes.
Now, long after the event, Timothy Krisher and his colleagues at the
Jet Propulsion Laboratory in Pasadena, California, have examined the record
of the signal from Voyager 1. The spaceprobe flew within 180 000 kilometres
of Saturn on 12 November 1980. They find that as the spaceprobe moved in
and out of the gravitational field of Saturn, its transmitter’s frequency
dipped. The dip was no more than a few hertz, but it was within 1 per cent
of the prediction of general relativity for a frequency of 2.3 gigahertz.
Fluctuations in the frequency of the transmitter – though very small – nevertheless
prevented the theory from being tested even more severely (Physical Review
Letters, vol 64, p 1322).
Krisher and his colleagues have yet to determine whether data from the
transmitter on board Voyager 2 can help them to test general relativity
further. It was badly affected by intense radiation as it passed by Jupiter
on its way to Saturn and so its data may not be as reliable as the data
from its predecessor. The current results may, however, rule out some alternatives
to Einstein’s theory.
https://www.newscientist.com/article/mg12517102-600-science-encounter-with-saturn-confirms-relativity-theory/ |
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