# Tag Info

33

As @Donald.McLean said in comments, the answer is yes, the Moon can and does occult the other planets in the Solar System. When something apparently big (like the Moon) passes in front of something apparently small (another planet) it's called an occultation. (I say apparently because from our perspective the Moon appears larger than the planets.) The ...

31

Venus has a strong ionosphere that protects it against violent solar winds. So, even though Venus has no intrisic magnetic field, it has an effective, induced magnetic field due to the interaction between the solar winds and the atmosphere, that protects it against solar winds. Venus atmosphere is thick enough to have a consequent ionosphere, that would be ...

28

@BMF's comment links to (Gold & Soter 1969) Icarus 11, (3), November 1969, pp 356-366 Atmospheric tides and the resonant rotation of Venus. Since it is paywalled I'll add a short summary: From the abstract: The observed spin-orbit resonance of Venus, whereby the same side of Venus faces the Earth at each inferior conjunction, cannot be explained ...

19

There seem to be a few, and none are accepted by the whole scientific community. The main ones: Venus was struck by a large body during its early formation The spin axis flipped, as can happen with a gyroscope The spin slowed to a standstill and then reversed, caused by the sun's gravity, the dense atmosphere and friction between core and mantle That final ...

14

There is an interesting article on the magnetosphere of Venus on the ESA Science and Technology site. You can find the article here and it will probably answer your question. The article states, like you did, that there are planets, like Earth, Mercury, Jupiter and saturn, have magnetic fields interland induced by there iron core. These magnetic fields ...

14

This is a fun little problem that's remarkably close and the math is pretty easy when you use the right periods. Venus' synodic period, relative to Earth, is 583.92 days on average. He uses 584, but lets strive for accuracy. Venus' solar day is 116.75 days, so 5 solar days is 583.75 days - Venus does 5 rotations in nearly the same amount of time that ...

13

The strength of the Earth's gravitational field compared to the Moon and the Sun is not enough to capture and hold satellites - there are too many disruptive forces that would rip them away over time. However there are some objects at the Lagrangian points - the points where the gravitational fields of the Earth and other objects are equal and so it is ...

12

This is a very interesting question. Of course, as you noted, you have simplified things quite a bit; there are other factors besides temperature that affect habitability. Regarding Venus, you probably know that Venus is extremely hot at its surface not just because it is closer to the Sun, but because it has a thick CO2 atmosphere and is warmed by the ...

12

Yes, such events are called occultations. The Moon can occult anything within about 5 degrees of the ecliptic. The visibility of any lunar occultation is limited to a path as wide as the Moon is. This EarthSky article discusses a series of lunar occultations of planets in September 2017, including Venus as seen from Australia. The article includes a photo ...

11

This is supplementary to antispinward's excellent answer and provides additional sources and a visualization from the JAXA spacecraft Atasuki. It has been shamelessly borrowed from Would it be possible to "ride the wave" on Venus? The recently published paper in Nature Geoscience Atmospheric mountain wave generation on Venus and its influence on the solid ...

10

Either or neither. It's impossible to tell from the present. If runaway climate change occurs, then yes, the conditions on Venus could be a potential analogue for the kind of environment on Earth due to the greenhouse effect. Mars's atmosphere is assumed to have been much thicker in the past, otherwise it could not have sustained liquid water on the ...

10

If you are asking about short-term effects related to human's effect on the climate, the answer is (obviously) unclear. But in the very long term, Earth is likely to evolve to a more Venus-like state. Over the next billion years or so, the Sun's luminosity will slowly increase, which will heat Earth's surface. As a result, more water vapor will evaporate ...

10

Before we begin: how far a planet is seen from the Sun is called elongation, and it's measured in degrees. 0° elongation means it's right on top of the Sun (or behind); 180° elongation means it's opposite to the Sun (it's highest in the sky at midnight, when the Sun is on the other side of the Earth). https://en.wikipedia.org/wiki/Elongation_(astronomy) ...

10

It has a low eccentricity, but there may not be a particular reason. Image by Kheider on wikipeda using Gravity Simulator by Trevor Dunn In a simulation of the solar system, both Earth and Venus had orbital eccentricities that were much below those of Mars and Mercury (note the two axes. Mars and Mercury are on a scale that is 10 times bigger). But in ...

10

This shape is usually known as the "Y feature" and it appears in the ultraviolet (most images of the Venusian atmosphere incorporate information from the ultraviolet because that provides the most detail). Peralta et al. (2015), "Venus's major cloud feature as an equatorially trapped wave distorted by the wind" describes the formation of the Y feature in ...

9

As others have calculated, there are no predicted double transits. Since Venus transits for about 12 hours each hundred years (roughly), Venus is in transit for about 1/100000 of the time. Thus there is a (roughly) 1 in 100000 chance that a randomly chosen transit of mercury will coincide with a transit of Venus. Since Transits of Mercury occur every 10 ...

8

There are other ways to lose atmosphere. For example Jean's Escape. If average velocity of a gas molecule exceeds escape velocity, the planet will lose atmosphere. Venus' atmopshere is mostly $CO_2$ which has a higher molecular weight than the $0_2$ and $N_2$ of our atmosphere. So, for a given temperature and pressure, the carbon dioxide molecules have a ...

8

It's unlikely that either Mercury or Venus could have moons to begin with. Both of these planets are pretty close to the Sun — and in general, this prevents moons from finding stable orbits. If a moon were too close to the planets, it would fall within the Roche limit and be torn apart by tidal forces. If a moon were too far from the planets, it would fall ...

8

You can think of it in terms of Hohmann transfer orbits, which define the minimum $\Delta v$ that needs to be applied to bring something from one orbital radius to another orbital radius when orbiting a massive body. This calculation takes into account that the two objects have Keplerian orbits where the objects begins with at least the orbital speed of the ...

8

Venus orbits the Sun at 0.723332 AU. As solar radiation follows an inverse square law, the intensity of the Sun at the top of Venus's atmosphere is almost twice that for the Earth ($\frac1{0.723332}^2\approx1.9113$). Even when the solar system was young and the Sun was considerably dimmer than it is now, Venus received 1/3 more solar radiation at the top of ...

7

My ad-hoc opinion: This wouldn't be the first step of Venus exploration. Geologic in-situ investigation of the resurfacing hypotheses would already be a very challenging mission. Might be, one could find some metamorphic remnants which have survived the last resurfacing, and one could determine the age of rocks. Might be there exist some old layers below the ...

7

This was originally going to be a comment, but it ran too long, so I'm making it an answer. Some models argue that the scenario of a satellite of Venus escaping like this is unlikely. Alemi & Stevenson (2006) have explored the possibility of a prior Venusian moon, starting from the assumption that Venus would not have been able to avoid a giant impact. ...

7

A planet's environment is a complex interplay of factors. If you dramatically change the insolation of a planet, it becomes very difficult to predict how the other factors which influence the planet's environment will respond. Venus, for example, seems locked into its high-CO2 environment (which makes its surface hot) because its surface is too hot to ...

7

I think you'll have to live with an incomplete answer. It appears this was taken by an amateur astronomer using a simple 4.5 inch telescope. You can find, on the ESO website, a collection of many images taken during the 2004 transit. On this page, is the image you are asking about (along with some other images by the same person). The credit for that image ...

6

Because planets actually do twinkle. Most people were told that the major difference between stars and planets is that only the former twinkle - but that's an oversimplification. Given the right conditions, planets will twinkle too, it just happens more rarely. Several factors that contribute to it: lots of air turbulence; or, as astronomers call it, "bad ...

6

No. According to the Nasa Venus fact sheet the density of the atmosphere at the surface is ~65 kg/m^3. For comparison, water is 1000 kg/m^3. We only just float in water. So if you were there, in a suit that could somehow withstand the heat (464 C), the "air" would feel thick. Maybe a person could strap on some wings and fly ...

6

This is a question that cannot be accurately answered. However, the closest to a honest and accurate answer would be that neither, since the Earth is going to "evolve" (curious choice of words) towards the Earth's fate. The presence of humans means any purely physical projections need to be taken with a grain of salt. Our ability to influence the planet ...

Only top voted, non community-wiki answers of a minimum length are eligible