# Tag Info

95

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 ...

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, ...

14

It looks like the Mariner 9 era. Based on a review paper by Watters et al. ("Hemispheres Apart: The Crustal Dichotomy on Mars"): "The north-south asymmetry ... was clear from the first global image mosaics of Mars returned in the 1970s by Mariner 9 (Mutch et al., 1976) and the Viking Orbiters." Other papers cite a 1973 paper by Hartmann ...

13

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

Well if no one is going to answer this I will. The answer is we don't know for sure. We speculate that there should be earth rocks on mars but until we 'see' one and analyze it we will not know for sure. The comments here all point to this answer. Mars hit with thousands of Earth rocks possibly containing life following asteroid impacte talks about the ...

9

In "The Planet of Doubt", Stanley G. Weinbaum, Astounding Stories, October 1935, there is a scene where Hamilton Hammond, leader of a expedition to the north pole of Uranus, explains his descision to set a southeastern course while searching for land: "I'll tell you. Did you ever look at a globe of the Earth, Pat? Then maybe you've noticed ...

8

Yes. The Southern polar ice cap has a covering of $\mathrm{CO_2}$ about 8 m thick that doesn't completely disappear in summer. It remains in "pits" of up to about 1km in diameter. The thinner dry ice layer in the North sublimes completely into the atmosphere in summer. [source]

7

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. ...

7

You did two things wrong, one minor, the other major. The minor thing that you did wrong was to chose the solar system barycenter as the target rather than the Sun. Use the Sun. The major thing you did wrong was to use a step size of 1477 minutes. That is (to within a minute) the length of a Mars sidereal day. The Sun will march across the horizon if you use ...

6

There are two answers to this, because the period "687" was known long before it was recognised as an "orbital period". The Babylonians knew by 600 BCE that Mars took 79 years to go through all 12 constellations 42 times, giving a period of 79/42 × 365.25 = 687 days. But they wouldn't have thought of this as an "orbit" (in the modern sense) since they ...

6

No. Tetanus is caused by a soil bacteria. You cannot get tetanus from rusty iron, if that iron has been sterilised. There are no Earth bacteria on Mars. As far as we can tell, there is no life of any kind on Mars.

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 ...

5

The placement of the center of the map is messed up, but it's nobody's mistake. From chapter 4 of The Surface of Mars: The elevation difference between the two hemispheres offsets the planet’s center of figure from its center of mass by 2.986 km as measured along the polar axis Regarding the question that is in the title ("Why are the hemispheres so ...

5

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 $R_E^2$: $cos(\theta) = \frac{... 5 You can find MOLA laser altimeter data here:https://pds-geosciences.wustl.edu/missions/mgs/megdr.html. The files are simple rectangular grids of differences between Martian "sea-level" and measure height at 1/128 degree resolution. If you have the latitude and longitude, it is quite straightforward to find the height. To view these files, you probably ... 5 It is certainly possible for rocks from Earth to be ejected and impact - and survive impact - on Mars. However, without doing specific isotopic analysis to determine the origin, one cannot simply look at a meteorite and determine its source body. No rovers that we have now have the capability to measure these isotopes. With that overview, it is much ... 5 Scientists think they have - the Mojave crater. Also see https://science.sciencemag.org/content/343/6177/1343 5 You are seeing them in color, it's an issue of the mechanics of your eyes. Eyes are made of rods and cones, cones seeing color, rods seeing greyscale. When you are looking through a telescope, your eye adapts to the low light conditions and the rods dominate the sensitivity. Jupiter appears much larger than both Mars and Venus, so your eye does not adapt ... 4 Let's do a bit of math: magnetic energy density is at least$u = \frac{1}{2}\frac{B^2}{\mu_0}$. The magnetic field at the surface of Earth is of the order of 30µT which gives us a magnetic energy density in the order of$10^{-3} J/m^3\$ Now we need to fill the entire volume of the planet and some surrounding space with this field in order to get some ...

4

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) ...

4

You are right. If Mars orbited in exactly the same plane as the Earth, instead of an S or a loop, we would see Mars moving prograde relative for the stars along the ecliptic, then slowing and stopping, moving retrograde for a few months, as Earth overtakes it, still on the ecliptic, then moving prograde again. But Mars doesn't orbit in the same plane, so it ...

4

Jezero crater is roughly 50 km across, and it is emplaced within the wall of Isidis crater ("basin"). Isidis itself has seen a lot of erosion, but it has been dated by lots of different people through the use of superposed crater counts (craters on top of it, with the number-age relationship tied to the Moon) to somewhere around 3.85–4.05 billion ...

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

SOLAR SYSTEM/SUN, ATMOSPHERES, EVOLUTION OF ATMOSPHERES | Planetary Atmospheres Numerous dust storms occur each Martian year and are generally classified according to size. From the smallest to largest, they are dust devils (<10−1 km2), local storms (∼103 km2), regional storms (∼106 km2), and planet-encircling storms (>106 km2). Local dust storms are ...

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 ...

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