This is a what-if? piece on sending a drone to Saturn's moon Titan a proposal by two private companies:
http://www.space.com/33412-nasa-aero...oon-titan.html
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This is a what-if? piece on sending a drone to Saturn's moon Titan a proposal by two private companies:
http://www.space.com/33412-nasa-aero...oon-titan.html
It is interesting that they would consider using the atmosphere on Titan to survey the planet rather than orbiting above the atmosphere.
HOW MARS' MOONS FORMED
CNRS
The origin of the two Martian moons, Phobos and Deimos, has been
uncertain. Owing to their small sizes and irregular shapes, they
strongly resemble asteroids, but no one has understood how Mars could
have captured them and made them into satellites with almost circular
and equatorial orbits. According to one theory, towards the end of
its formation Mars suffered a collision with a proto-planet; but then
why did the debris from such an impact create two small satellites
instead of one relatively enormous one, like the Earth's? Another
possibility is that Phobos and Deimos formed at the same time as Mars,
which would entail their having the same composition as their planet,
although their low density seems to contradict that idea.
Two independent studies are now considered to have solved the puzzle:
the Martian moons must have arisen from a giant collision 100 to 800
million years after the beginning of the planet's formation.
According to one study, the debris from the collision formed a very
large disc around Mars, made up of a dense inner part composed of
matter in fusion, and a very thin outer part primarily of gas. In the
inner part of the disc was formed a moon a thousand times the size of
Phobos, which has since disappeared. The gravitational interactions
created in the outer disc by that massive moon could have acted as a
catalyst for the gathering of debris to form other smaller, more
distant moons. After a few thousand years, Mars was surrounded by a
group of approximately ten small moons and one enormous one. A few
million years later, once the debris disc had dissipated, the tidal
effects of Mars brought most of the satellites back down onto the
planet, including the very large moon. Only the two most distant
small moons, Phobos and Deimos, remained.
In a second study, researchers ruled out the possibility of a capture
by statistical arguments based on the compositional diversity of the
asteroid belt. They show, moreover. that the spectra of Phobos and
Deimos are incompatible with that of the primordial matter that formed
Mars (meteorites such as ordinary chondrite, enstatite chondrite
and/or angrite). They therefore support the collision scenario. The
spectra indicate that the satellites are made of fine-grained dust
(smaller than a micrometre). Yet the very small size of grains on the
surface of Phobos and Deimos cannot, according to the researchers, be
solely explained as the consequence of erosion from bombardment by
interplanetary dust. That means (they say) that the satellites were
from the beginning made up of very fine grains, which can only form by
gas condensation in the outer part of the debris disc (and not from
the magma present in the inner part). Both studies are in agreement
on thar point. Moreover, the formation of Martian moons from very
fine grains could also be responsible for a high internal porosity,
which would explain their surprisingly low densities.
The theory of the giant collision, which is advanced by the two
independent studies, could explain why the northern hemisphere of Mars
has a lower altitude than the southern hemisphere: the Borealis basin
is most probably the site of a giant collision, such as the one that
gave birth to Phobos and Deimos. It also helps to explain why Mars
has two satellites instead of a single one like our Moon, which is
also supposed to have been created by a giant collision. The research
suggests that the satellite systems that were created depended on the
planet's rotational velocity, because at the relevant time the Earth
was rotating very quickly (in less than four hours), whereas Mars
turned six times more slowly. New observations will soon make it
possible to know more about the age and composition of the Martian
moons. Japan's space agency (JAXA) has decided to launch a mission in
2022, named Mars Moons Exploration (MMX), which will bring back
samples from Phobos in 2027. Their analysis could confirm or
invalidate the new proposal. ESA has planned a similar mission in
2024 in association with the Russian space agency (Roscosmos).
It is good they have hypotheses test. I remember hearing, but don't know where that information came from, that the collision of the Earth with the other object that created the moon sent the Earth into its spin. Based on this it looks like the spin rate started earlier and was very fast and then slowed down.
SMALL ASTEROID IS THE EARTH'S CONSTANT COMPANION
NASA
A small asteroid has been discovered in an orbit around the Sun that
keeps it as a constant companion of the Earth, and it will remain so for
centuries to come. As it orbits the Sun, the new-found asteroid,
designated 2016 HO3, appears to circle around the Earth as well. It is
too distant to be considered a true satellite of our planet, but it is
the best and most stable example to date of a near-Earth companion.
Since 2016 HO3 loops around our planet, but never ventures very far away
as we both go round the Sun, we refer to it as a quasi-satellite of
Earth. One other asteroid -- 2003 YN107 -- followed a similar orbital
pattern for a while over 10 years ago, but it has since departed from
our vicinity. The new asteroid is much more locked onto us. Calcula-
tions indicate 2016 HO3 has been a stable quasi-satellite of the Earth
for almost a century. In its yearly orbit round the Sun, the asteroid
spends about half the time closer to the Sun than the Earth is, and
passes ahead of our planet, and the other half of the time farther away,
causing it to fall behind. Its orbit is also tilted a little, causing
it to pass up and then down once each year through the Earth's orbital
plane.
The asteroid's orbit also undergoes a slow, back-and-forth twist over
multiple decades. The asteroid's loops around the Earth drift a little
ahead or behind from year to year, but when they drift too far forward
or backward, the Earth's gravity is just strong enough to reverse the
drift and hold onto the asteroid so that it never wanders farther away
than about 100 times the distance of the Moon. The same effect also
prevents it from ever approaching much closer than about 38 times the
distance of the Moon. In effect, the small asteroid is caught in a
little dance with the Earth. Asteroid 2016 HO3 was first observed on
2016 April 27, by the Pan-STARRS 1 asteroid survey telescope in Hawaii.
The size of the object has not yet been firmly established, but it is
probably between 40 and 100 metres.
It looks like the earth has a tiny moon we didn't know about.
Here is another astounding fact:
The SOCIETY for POPULAR ASTRONOMY
Electronic News Bulletin No. 426 2016 July 17
DWARF PLANET MAKEMAKE HAS MOON
Southwest Research Institute
Scientists have discovered a dark moon orbiting Makemake, one of the
'big four' dwarf planets populating the Kuiper-Belt region at the edge
of the Solar System. The moon -- presently called MK2 -- is 1,300
times fainter than the dwarf planet. A nearly edge-on orbital
configuration helped it evade detection, placing it deep within the
glare of the icy dwarf during a substantial fraction of its orbit.
Makemake is one of the largest and brightest known Kuiper Belt Objects
(KBOs), second only to Pluto. The moon is probably less than 100
miles in diameter while Makemake itsef is about 870 miles across.
Discovered in 2005, Makemake is shaped like a football (notice that
this item was drafted in America, where footballs are not spheres) and
sheathed in frozen methane. With a moon, we can calculate Makemake's
mass and density and contrast the orbits and properties of the parent
dwarf and its moon, to understand the origin and history of the
system. We can compare Makemake and its moon to other systems, and
broaden our understanding of the processes that shaped the evolution
of the Solar System. With the discovery of MK2, all four of the
currently designated dwarf planets are known to have one or more
satellites. The fact that Makemake's satellite went unseen despite
previous searches suggests that other large KBOs may have hidden
moons. Before this discovery, the lack of a satellite for Makemake
suggested that it had not suffered a severe impact in the past. Now,
scientists will be looking at its density to determine whether it was
formed by a collision or whether it was grabbed by the parent dwarf's
gravity. The apparent ubiquity of moons orbiting KBO dwarf planets
supports the idea that collisions are a near-universal feature in the
histories of those distant objects.
So can we pretend to land on that one, too? ;-)Quote:
Originally Posted by YesNo
Well that one is rather small and it might not stick around.Quote:
Originally Posted by Pompey Bum
Yes, but could we fake not going there?
We could pretend it's the planet where le petit prince came from. Being only 100 meters in size where size is what? Diameter or circumference?
Be my guest, YN. Once the pretending begins, why should the sky be an obstacle?
That's how I look at the pretend manned Moon landings of the early 1970s. Land one of them and you might as well land another handful of them in rapid order.
So why should faking this little moon be any harder? Surely fake rocket telemetry has only improved since 1969?
Interesting about the near earth companion. Wise money has to go down on the side that says it is only a matter of time before our observations and calculations uncover cosmic calamity waiting for us that is still decades away. We will have time to act like fools.
Our solar system orbits the galaxy every 200,000 years. There could be a lot of "strange" space ahead of us. At least there will be a different view in 100,000 years. I can't wait.
I think it is more difficult to fake a moon landing today because of improved technology. Also there is no political reason to do so.
Regarding having a different view 100,000 years from now, aren't all the objects in the solar system and our portion of the galaxy coming along with us as we circle the galaxy?
Well, I sure don't want Chinese faking getting ahead of ours.Quote:
Originally Posted by YesNo
The fact that information can be faked requires skepticism as well as skepticism against skepticism. It is usually good to ask why someone wants you to believe something. Do they have a political, metaphysical or religious position they want to promote? If so, focus on that. Are they trying to sell you a stock? Are they trying to distort their country's gross domestic product to keep investors happy. Are they trying to claim there are weapons of mass destruction to get their people demanding a war of intervention?
What impresses me about the links that Dreamwoven provides in this thread is how little we know about the universe. Sure, we know simple things, as well as we can know them, such as the microwave background, because there is little there to know, but we are not aware of the objects in our solar system let alone the immediate region of our galaxy.
Thank you YesNo, much good sense.
http://earthsky.org/space/protoplane...t-mare-imbrium
There are lots of large asteroid blasts on the moon and other rocky planets. This is one that has been discussed.
Good point, YN. If I'd have known how much money my oncologist would made off of my cancer treatment, I never would have let her talk me into it. If only I'd had your advice then...Quote:
Originally Posted by YesNo
I don't see what this has to do with an astronomy thread.Quote:
Originally Posted by Pompey Bum
You're the one who brought it up.Quote:
Originally Posted by YesNo
I had not considered the Mare Imbrium to have been originally made by an impact, but it does look circular. After that impact I assume there was a lava flow of some sort.Quote:
Originally Posted by Dreamwoven
That is something I haven't considered. The moon has no atmosphere so there is no resistance on entry. In that case there would be no lava flow. The impact crater might generate enough heat to create a lava flow, though. I think this needs a lot of further thought and analysis.
N=R*x fp x ne x fl x fi x fc x L
Has this ever been discussed, and is it suitable for this thread?
I don't know what this relationship is meant to represent.Quote:
Originally Posted by desiresjab
Regarding the lava flow, one would have an impact crater on an active planet. Sometime later the depression of the crater would be filled with lava. https://en.wikipedia.org/wiki/Lunar_mare
http://www.space.com/33494-nearby-ea...ets-rocky.html
This page from the Space website shows Hubble still gathering useful info:
Thanks, Patty.
I have been thinking of all those astronomy-interested who invest in telescopes and equipment. But we have our own moon which can be examined without any aids at all. And it is always there visible to every part of the world. This post looks at one aspect of the moon: http://www.space.com/33491-mysteriou...t-impact.html?.
I didn't notice the Imbrium Sculpture before, but now that I think of Mare Imbrium being the result of a collision it seems obvious.
Now that the probe called Juno is in orbit around Jupiter we are already starting to get more information on that huge planet: http://www.space.com/33551-jupiter-h...-red-spot.html.
So strange the amount of heat from the Great Red Spot. Perhaps vortices above a super-super-super volcano ?, but that wouldn't account for an acoustical component... Can't wait to find out !
Ta ! (short for tarradiddle),
tailor STATELY
Now I know there exist things like gravity and acoustic waves and the upward coupling of the lower and higher atmosphere assuming these explanations are correct.
Yes and this at the start of the Juno Mission!Quote:
Originally Posted by tailor STATELY
I'm not convinced by the arguments in the link of the previous post. We all know that the larger the object the more likely it will capture meteorites, in part by its much greater gravitational pull. This is why the big outer planets have many moons and why Jupiter sucks to it larger meteorites. A small dwarf planet, without even a moon, will have a relatively quiet and calm history. Nothing strange about that.
What I most expect and predict as the connundrum is failure of the model to accurately reflect the personal history of each asteroid. No surprise at all, since their lives do not look to have been so quiet to me. Belts still have thickness. An interior portion is hit by less debris, certainly by fewer large chunks hurling in from outside the belt. This, as well, means fewer big collisions on these interior bodies of the belt. I have to assume these scientists are top guns and have already considered all this and more, which would make the solar flyby coming up quite exciting to them.
Here is a double-double star: http://earthsky.org/brightest-stars/...le-double-star
Apparently they can be seen with binoculars!
I've noticed Vega before in the constellation Lyra, but I didn't realize there were double double stars like Epsilon Lyrae.
This item in EarthSky was published today: http://earthsky.org/space/star-lashe...th-mystery-ray.
No idea what they mean by pulsing neutron star.