# Tag Info

22

I feel it's a cheap answer but heavy Jupiters can get much denser than Earth because planets with Jupiter's mass stop adding size as they add more mass. A planet with Jupiter's size and 10-12 times Jupiter's mass would be over twice Earth's density. As far as Earth-like planets, there's a cool property of terrestrial planets, more mass means more tightly ...

10

The two hemispheres have distinctly different appearances, with the near side covered in multiple, large maria (Latin for 'seas,' since the earliest astronomers incorrectly thought that these plains were seas of lunar water). The far side has a battered, densely cratered appearance with few maria. Only 1% of the surface of the far side is covered by maria, ...

10

There is no reason it should be. There are bound to be irregularities due to local geological differences. EDIT: The theory as to why planets tend to be spherical is because any irregularity would cause a non-uniformity in the gravitational field at the surface, and the forces on the surface rocks would ultimately cause it to be spherical. Though, ...

9

There are a few factors that create this effect: First in the visual light images, the view around the equator is seen back lit, with almost no shadow, the few around the pole is seen with low lighting, and low lighting brings out features of the terrain. The Polar mosaics have an unreal quality, since they are made of images all taken when the sun is ...

8

I'm doing some palaeobiology-landscape rendering; so I'm thinking if I want to add the sun in such pictures; should I draw it just like present day ? Although the Sun was less luminous 4.5 billion years ago (about 70% of it's current luminosity, it is thought), and while this would affect it's color, making it perhaps a little more orange than yellow, the ...

8

From the wikipedia page on Chthonian planet https://en.wikipedia.org/wiki/Chthonian_planet "Transit-timing variation measurements indicate for example that Kepler-52b, Kepler-52c and Kepler-57b have maximum-masses between 30 and 100 times the mass of Earth (although the actual masses could be much lower); with radii about 2 Earth radii, they might have ...

7

There is a nice article from Scientific American, but the main point is: There are three main sources of heat in the deep earth: (1) heat from when the planet formed and accreted, which has not yet been lost; (2) frictional heating, caused by denser core material sinking to the center of the planet; and (3) heat from the decay of radioactive elements. ...

5

You can divide this into two astronomical epochs, which are most easily understood in terms of the Hertzsprung-Russell diagram. The first is the pre-main-sequence (PMS) phase, where the protosun contracts towards its main sequence, hydrogen burning, configuration. During this phase the (proto-)Sun declines in luminosity at roughly constant temperature for ...

5

Planets and moons are never going to be completely homogenized such that their radial density is perfectly spherically symmetric. They're always going to have mass concentrations (mascons) with regions of more mass than average. These mascons, due to the extra mass, cause gravitational anomalies of higher gravity in those local regions. These mascons exist ...

5

If we look at Mars' possible geothermal gradient (see Earth's) which is about 25 °C per km. Using the low estimate of Mars's gradient to be 1/4 that of Earth's Source, that's a bit over 6° C per km. so 55 km, 330° C. Added that to Mars' average surface temperature of -55 C, you're talking 275° C or 527° F at 55 km underground, and that's a low estimate. ...

5

Shape of Earth is geoid. It's because of the rotation of our planets around its axis. Because of the centrifugal force, the diameter of Earth is bigger at the Equator than at the (physical) North Pole. Billions of years of rotating have deformed the perfect shape form of Earth - if it has ever had at all.

4

I would say that your initial observation is flawed, so the question is moot. Huygens landing site, Titan:

4

From a simplistic point of view the rate of cooling depends on the ratio of surface area to volume. It is complicated by the rate of heat transfer of various layers, and internal sources of "new" heat in addition to the heat generated when the planet formed. The main way heat is lost is radiation to space. The atmosphere itself acts a a kind of "blanket" ...

4

The velocity required to escape the gravitational attraction of a massive body is given by the following equation: $$v_{\mathrm{escape}} = \sqrt{\frac{2GM}{R}}$$ where $G$ is the gravitational constant ($G = 6.67 \times 10^{-11} \; \mathrm{Nm^{2} {kg}^{-2}}$), $M$ is the mass of the body from which you are escaping, and $R$ is its radius. Inputting the ...

3

The geological term mesa has been used to describe these structures. A transitional zone on Mars, known as the fretted terrain, lies between highly cratered highlands and less cratered lowlands. The younger lowland exhibits steep walled mesas and knobs. The mesa and knobs are separated by flat lying lowlands. They are thought to form from ice-facilitated ...

3

I don't know what you're talking about. The only one that seems to have mostly flat rocks is Venus. At least based on what little photographs we have from the surface of Venus. Mars Venus

3

Io is not dominated by sulfur. Io is mostly silicate rock and iron. Sulfur is a thin coating on the surface and sulfur dioxide makes up most of the atmosphere, but that's because sulfur dioxide is a volatile. In other words, it has a much lower melting and boiling point than silicate rock. So while the rock remains solid, the sulfur dioxide is gas. Carbon ...

3

The MESSENGER probe was able to take many true-color pictures of Mercury. A full list can be found on JPL's Photojournal. It is clear that Mercury is light grey in color. (source: nasa.gov) (source: nasa.gov) (source: nasa.gov) In terms of the actual surface, Mercury is very similar to the Moon. It's surface is speckled with craters, with some ...

2

You could probably get away with replacing molten iron, 7.87 g/cc, in the core with aluminum, 2.70 g/cc, and still generate a substantial magnetic field: Molten Metal Magnet It’s easy to create a magnetic field by using a battery to force an electric current through a loop of wire. But Earth’s core, a rotating mix of iron and nickel with internal flows ...

2

It looks like you are asking about rubble piles, asteroids that are made up of a large number of different sized objects that are weakly held together by gravity. A few of the component objects are large, but most are very small (down to grains of sand). By way of analogy, think of playing pocket pool. Rack the 15 target balls but leave the rack on. The cue ...

2

We actually know a number of elements present on the lunar surface including oxygen, silicon, iron, magnesium, calcium, aluminium, manganese and titanium. We have also observed that carbon and nitrogen have deposited over time from solar wind.

2

Planet solidifying. No molten core iron -> no magnetosphere -> solar wind strips atmosphere. Without atmosphere to cycle in exposed water also leaves. Why did Mars freeze solid & Earth has not (yet). is further from sun smaller means less volume to hold heat Earth may have the iron cores from two planets (moon forming impact) Radioactive decay? On ...

2

From another question on the stack exchange I just found out about an exoplanet with a much higher density than Earth: Kepler-131c. https://es.wikipedia.org/wiki/Kepler-131c Sorry for the WP page being Spanish, there is no English one.

1

The need to distinguish between these potato-shaped and spherical moons hasn't arisen. As such, there aren't two different words to designate these two types of moons. And as long as the community of astronomers who study natural satellites doesn't feel the need for there to be an extra category, there likely won't be one created preemptively. Perhaps, one ...

1

Based on assumptions, if you are ok with approx solution then you can solve heat transfer equation in steady state. Heat transfer equation Ignoring the time - long time has passed to attain equilibrium. Heat flux assuming outward and hence internal ocean would be sum of all internal heating mechanism. Easiest would be if somehow you can come up with ...

1

If you peruse Google for Earth cooling rates, you might find what you're looking for. Here's one of many sources. I strongly recommend reading the entire page,as it discusses some of the geology-based estimates as well. Kelvin's primary attack on geologic dating was that measurements of the rates of geologic processes were highly uncertain, if it was ...

1

Nobody knows it. 55 km depth is probably between crust and mantle, with estimated temperatures well above 500 K.

1

When the Sun is on the meridian and is due South (local noon in Northern Hemisphere) your hour hand will point to (or close to 12) - assuming your local noon and civil noon are similar! (Daylight saving means 1pm fills this role). The Sun crosses the sky in 24 hours, the hour hand travels round the watch in 12 hours. Hence the watch hour hand is twice as ...

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