# Tag Info

23

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 ...

13

Berman and Hartman (2002) dated some lava flows of the Athabasca–Marte Valles system at < 20 Ma. Later, Vaucher et al. (2009) dated lava flows of the same region, finding ages even younger in some cases (around 2.5 Ma). In both studies the age estimates are derived from surface morphology (crater counts). In Volcanoes: Global Perspectives, Lockwood & ...

11

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 ...

9

From the Wikipedia page on 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 densities larger than that of an iron planet of the ...

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

As pointed out in the comments, some do prefer to use different terms for quakes on other bodies, and you can see here that "marsquake" does have scholarly usage. That said, there is also scholarly usage for "earthquake" in this context. If you think about it, this makes sense given that one definition of "earth" is "the substance of the land surface", i.e. ...

8

A key requirement for caves is solid substance: while there may be rock cores inside the giant planets, the rest is liquid or gas. Metallic hydrogen may be solid or liquid in Jupiter, but presumably the pressure is high enough to prevent cave formation. So no for Jupiter, Saturn, Uranus and Neptune. A second requirement is some factor digging cavities. On ...

8

There are several ways to look at this. One rather simple way is to compute the Rayleigh number of Mars' mantle. The Rayleigh number is a dimensionless number defined as: $Ra = \dfrac{\rho g \alpha \Delta T d^3}{\eta \kappa}$ where $\rho$ is the mantle density, $g$ is gravitational acceleration, $\alpha$ is the thermal expansion coefficient, $\Delta T$ is ...

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. ...

7

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. ...

6

Great question! The mare lava bubbled up through fractures in the floor of the crater, burying its ring system and central peak.

6

This is the latest catalogue from seismic events recorded by InSight: Mars Seismic Catalogue, InSight Mission; V5 2021-01-04. This report includes seismic events up to October 12, 2020. These documents get periodicaly published, so keep an eye on the page pointed out by @planetmaker on the comments. The robot has measured a total of 1759 Marsquake events as ...

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

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

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 ...

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

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 smaller ...

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

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 ...

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

Ishtar Terra belongs to the tessera type of terrain, "one of the most tectonically deformed types of terrain on Venus", representing ~7.3 % of Venus' surface (Ivanov & Head 2011, Global geological map of Venus). Tessera are "dated" (relatively, from stratigraphic relationships) from the Fortunian, the oldest period: The most ...

3

This source from NASA says: Most scientists think the the cliffs formed by landslides. This collapse is driven by the weight of the huge volcano exceeding the strength of the rocks it is built of. In other words, one theory is as you have surmised: The outer 7km shell of the volcano appears to have slid down, all around the mountain, forming the cliffs. ...

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