- 3973 - MARS - has two moons! Mars's two moons, Phobos and Deimos, have puzzled researchers since their discovery in 1877. They are very small: Phobos's diameter of 22 kilometers is 160 times smaller than that of our moon, and Deimos is even smaller, with a diameter of only 12 kilometers.
---------------------------------- 3973 - MARS - has two moons!
- Our moon
is essentially spherical, while the moons of Mars are very irregularly shaped,
like potatoes. Phobos and Deimos look
more like asteroids than natural moons.
-
- Maybe they might in fact be asteroids that were
captured in Mars's gravity field.
Captured objects would be expected to follow an eccentric orbit around
the planet, and that orbit would be at a random inclination. In contradiction
to this hypothesis, the orbits of the Martian moons are almost circular and
move in the equatorial plane of Mars.
-
- So, what is
the explanation for the current orbits of Phobos and Deimos?
-
- To solvethis
problem the idea was to trace the orbits and their changes back into the
past, The orbits of Phobos and Deimos
appeared to have crossed in the past.
This means that the moons were very likely in the same place and
therefore have the same origin.
-
- The
researchers concluded that a larger celestial body was orbiting Mars back then.
This original moon was probably hit by another body and disintegrated as a
result. Phobos and Deimos are the
remainders of this lost moon.
-
- The
researchers had to refine the existing theory describing the interaction
between the moons and Mars. All the
celestial bodies exert tidal forces on each other. These forces lead to a form of energy
conversion known as dissipation, the scale of which depends on the bodies'
size, their interior composition and not least the distances between them.
-
- Mars is
currently being explored by NASA's InSight mission. Other Mars probes have suggested that Phobos
and Deimos are made of very porous material.
-
- At less
than 2 grams per cubic centimeter, their density is much lower than the average
density of Earth, which is 5.5 grams per cubic centimeter. There are a lot of
cavities inside Phobos, which might contain water ice and that's where the
tides are causing a lot of energy to dissipate."
-
- Using these
findings and their refined theory on the tidal effects, the researchers ran
hundreds of computer simulations to track the orbits of the moons backward in
time until they reached the intersection the moment Phobos and Deimos were
born.
-
- Depending
on the simulation, this point in time lies between 1 and 2.7 billion years in
the past. The exact time depends on the
physical properties of Phobos and Deimos, that is, how porous they are.
-
- A Japanese
probe scheduled for launch in 2025 will explore Phobos and return samples to
Earth. The researchers expect that these samples will provide the needed
details about the interior of the Martian moons that will enable more precise
calculations of their origin.
-
-
Calculations show is that the common ancestor of Phobos and Deimos was
further away from Mars than Phobos is today. While the smaller Deimos has
remained in the vicinity of where it came into being, tidal forces are causing
the larger Phobos to approach Mars, and this process is ongoing.
-
- Computer
simulations also show the future development of the moons' orbits. It seems
Deimos will move away from Mars very slowly, just as our moon is slowly
receding from Earth. Phobos, however, will crash into Mars in less than 40 million
years or be torn apart by the gravitational forces as it nears Mars.
-
April 25, 2023 MARS - has
two moons! 3973
----------------------------------------------------------------------------------------
----- Comments
appreciated and Pass it on to whomever is interested. ---
--- Some
reviews are at: -------------- http://jdetrick.blogspot.com -----
-- email
feedback, corrections, request for copies or Index of all reviews
--- to: ------
jamesdetrick@comcast.net
------ “Jim Detrick” -----------
--------------------- --- Tuesday, April 25, 2023
---------------------------
-
No comments:
Post a Comment