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94

Firstly, Mars has a mean distance from the Sun of 1.524 AU, so by the inverse square law the energy it gets from the Sun is about 40% of what the Earth gets. But the main reason that Mars is so cold is that its atmosphere is very thin compared to Earth's (as well as very dry, see below). From Wikipedia Atmosphere of Mars: The atmosphere of Mars is much ...


34

Forget about magnification. People who know telescopes don't think in terms of magnification. What matters is the angular resolution, or the resolving power: the angular size of the smallest details that you could see in an instrument. Rule of thumb: the resolving power of a telescope with a diameter of 10 cm is 1 arcsecond when using visible light. The ...


27

I'm just going to expand and deepen on what the other answers already said. In the following I contrast the atmospheric transmission ($T$) and absorption ($A$, which is $A=1-T$) of Mars and Earth. The Mars plot (top) is from Prof. J. Irwin via this review by P. Read et al. 2015 and the terrestrial data (bottom) is from wikipedia. The plots of $A$ and $1-T$...


16

Mars does have a greenhouse effect, only somewhat weaker than Earth's. Mars' atmosphere is very dilute, with a with a surface pressure only 0.6% of Earth's. So even if 95% of it is CO2, that's not a lot. However, it is actually a higher absolute abundance of CO2 molecules than on Earth, which only has a CO2 abundance of 0.04% (by volume; e.g. NOAA, ...


12

Are Tharsis Montes and Hellas Basin a result of the same event? You were not the first to have seen that the Hellas Basin and parts of the Tharsis Rise are roughly antipodal (Peterson 1978, Williams and Greeley 1994). The Tharsis Montes themselves are far too close to the equator to be considered antipodal to the Hellas Basin. The shield volcano Alba Mons ...


10

The Hubble space telescope has a 2.4m mirror and is pretty much diffraction limited, so at near-UV wavelengths of say 240nm it has an angular resolution of about $10^{-7}$ radians. Mars' closest distance to Earth is about 54.6 million km, so the theoretical minimal resolution is between 5 ad 6 km. So large cities might be visible if they have lots of ...


9

Such transit events occur when Earth and Mars are simultaneously at a node where their orbital planes intersect. Between transits at the same node, both Earth and Mars must complete whole numbers of orbits, where 1 Mars year = 1.8808 Earth years. Meeus and Goffin 1983 identify patterns of 79-year and 284-year intervals: 79.0 Earth years ≈ 42.0 Mars ...


8

The oceans would be smaller because Mars has lost most of its water. From Wikipedia's article on the Martian polar ice caps: Evidence that Mars once had enough water to create a global ocean at least 137 m deep has been obtained from measurement of the $HDO$ to $H_2O$ ratio over the north polar cap. In March 2015, a team of scientists published ...


6

Let us first consider the Earth a fixed point and Mars moving around the Sun on a circular orbit with angular velocity equal to the relative angular velocity ($\omega_\bigoplus - \omega_♂)$ The distance between Mars and the Earth can be described as the square root of $R_E^2+R_M^2-2R_ER_Mcos(\theta)$, and when this is equal to $R_E^2$: $cos(\theta) = \frac{...


6

As far as I know, "seeing" (or rather the effects influencing optical wave propagation) is caused by turbulence in the atmosphere. Using the Reynolds number Number $ Re = \dfrac{\rho L v}{\mu}$ as a measure for turbulence: density $\rho$ drops due to the reduced pressure (about 1/100 earth pressure), additionally the gravity is smaller than on earth ...


6

First Shooting Star Seen from Mars space.com 2005 The background image shows the meteor near the top-left and the horizon at the bottom. A red arrow shows the direction of travel. The inset is a larger version of the meteor itself. The graph is a "light curve" that aided in tying the meteor to comet Wiseman–Skiff. (Image: © Nature/NASA/Spirit/F. ...


4

Phobos' shadow on Mars is very narrow -- only about 15 miles across -- and it didn't quite pass across the Sun as viewed from the lander on that particular orbit. This image (taken by Mars Global Surveyor) gives you an excellent picture of just how small it is: Credit: NASA/JPL/Malin Space Science Systems Source The penumbral shadow of Phobos is ...


4

This is considered very unlikely. It is actually very difficult for things to be captured into orbits. They pick up speed as they fall in towards the larger object, and that's automatically enough speed to carry them back out. Capture either requires dust and gas to slow the body down, or very lucky gravitational interaction with a third object. This has ...


4

A lot of the water ice on mars is covered with dust. NASA's Phoenix mars lander only had to scrape off some of it to find the layer of ice underneath as seen here: https://www.nasa.gov/mission_pages/phoenix/images/press/sol_020_024_change_dodo_v3.html


4

You can find MOLA laser altimeter data here:https://pds-geosciences.wustl.edu/missions/mgs/megdr.html. The files are simple rectangular grids of differences between Martian "sea-level" and measure height at 1/128 degree resolution. If you have the latitude and longitude, it is quite straightforward to find the height. To view these files, you probably ...


3

Short answer: the Earth is closer to the Sun than to Mars about 77.9% of the time. Methodology I wrote https://github.com/barrycarter/bcapps/tree/master/ASTRO/bc-compdist.c to compute when and how long Mars was further from the Earth than the Sun. In the ~30,000 year period covered by DE431, this happens 14,231 times for an average duration of 607.93 days, ...


3

For a diagramatic answer, draw a circle around the Earth of 1AU radius, place the Sun on that circle then draw Mars' orbit. The part of Mars' orbit that is outside the 1AU circle is the part where Mars is farther away than the Sun. I expect that the two current answers are equivalent.


3

Giovanni Cassini used parallax with a friend, from two different sides of the Earth. It was generally accepted that the stars didn't move relative to each other or relative to the motion of the Earth. The planets moved, the stars didn't. Cassini was before Newton but after Kepler, so he had access to Kepler's 3rd law which is the law of periods, which ...


3

There are hard limits on what types of gas that Mars can retain based on its temperature and mass (Graph of what gasses an astronomical body can retain). Volume wise, it's not clear. Currently Mars is still losing its atmosphere, so it can't even retain that amount of atmosphere. But if you continually added gas to Mars, there isn't an end point where the ...


3

This is one of key questions that NASA's Mars InSight probe is trying to answer but it has only recently arrived and starting taking data and it will be a while before the data is analyzed and published in peer reviewed journals. The "mole" which would burrow below the surface and make the temperature measurements encountered some initial issues and NASA and ...


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

Unfortunately, there was a server problem in the days leading up to the exciting Mars occultation. (It didn't matter to me because it was, unfortunately, cloudy where I live.) This description of the colored lines is from a temporary page provided by IOTA: The turquoise curves show where the disappearance or reappearance occurs at moonrise (left side) ...


2

The eclipse on sol 2359 occurred at 03:45 UTC on 2019-03-27, and Curiosity saw Phobos pass wholly in front of the northern half of the Sun. The post-sunset eclipse on sol 2358 occurred 23 hours or 3 Phobos orbits earlier, around 04:49 UTC on 2019-03-26. This time Phobos passed a little farther north, casting its shadow mostly to the north of Curiosity while ...


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

You can do it, I will leave you to decide whether you should... As an experiment, I downloaded the mrox_3374 subdirectory of files and the result came out to 3.7 GB. Assuming the other 99 "volumes"/directories are the same, this multiplies out to 370 GB. I downloaded these data using wget which is a standard utility on Unix/Linux and Mac computers. It is ...


2

One hypothesis: at first there is a rapid decrease in albedo, which is then followed by a rapid increase. The decrease could be due to dust contamination after all the CO2 frost sublimation; as temperature continues to rise up, dust could thermally sink into the water–ice and/or fall into cracks between larger grains of water–ice A conceptual ...


1

Obliquity anything from 11 - 28 degree swings which would obviously affect seasonal changes. Is this a fact (where's the evidence) or "scientific fable". I don't like to use the word fact in a situation like this. What that variation is, is a mathematical model based on well understood but pretty complicated n-body gravitational perturbations between ...


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