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95 votes
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Why is Mars cold?

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 ...
PM 2Ring's user avatar
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38 votes

Please check my Mars photo

(Much of this echoes what antlersoft says in their answer) For a phone photo through the eyepiece that looks about right to me! The size... the brightness... both are as I expect. What you could try ...
Aaron F's user avatar
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34 votes
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What detail can Hubble see on Mars?

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 ...
Florin Andrei's user avatar
30 votes
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Which planet is this (if any)?

Stellarium shows the Moon and Mars very close together in the sky tonight (Saturday, 3rd October 2020), so yes, it was probably Mars that you saw. Moon and Mars on 2020/10/03 (Stellarium) Stellarium ...
Mick's user avatar
  • 1,546
26 votes

Why is Mars cold?

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. ...
AtmosphericPrisonEscape's user avatar
25 votes

Which is brighter, Mars as seen from Earth, or Earth as seen from Mars?

We can use the expression that is commonly used to estimate the apparent magnitude of a planet or asteroid in the Solar System: $$\boxed{m=5 \log \frac{1329}{d \cdot \sqrt p}+5 \log (D_s \cdot D)-2.5\...
Albert's user avatar
  • 2,102
24 votes

Are there lightning bolts on Mars?

Lightning may have been detected on Mars, although it currently appears to be rare, and attempts to replicate the 2006 results have failed so far. New research found that the low pressure on Mars ...
IronEagle's user avatar
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24 votes
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On Mars, why are the seasons "strongly amplified" in the southern hemisphere and masked in the northern hemisphere?

Your solution is correct. Mars has a perihelion that is, coincidentally, quite close to the southern Hemisphere summer solstice. Perihelion is actually about one (Earth) month before the solstice. ...
James K's user avatar
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23 votes
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Martian Constellations

The stars are so immensely far away that to the human eye there would be no noticeable difference. The nearest stars are moving roughly 1.5 arcsecond wrt. the background when viewed from Earth's ...
pela's user avatar
  • 38.6k
20 votes

Please check my Mars photo

It's very difficult to get any kind of picture just holding your phone up to the eyepiece, and the picture you posted is overexposed and probably motion-smeared, but other than that it's what you'd ...
antlersoft's user avatar
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19 votes
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How could Mars' atmosphere be shed by solar winds, when Venus has a thick atmosphere despite no magnetic field?

I am not certain that the main cause of Mars losing most of its atmosphere was the solar winds. Long before the solar wind was discovered scientists calculated other factors which affect how long a ...
M. A. Golding's user avatar
16 votes

Whats the probability of a hazardous impact for human life on Mars?

We actually have a very good idea of this because the Mars Reconnaissance Orbiter has been orbiting Mars for over a decade. The MRO is, basically, a spy satellite around Mars and is continually taking ...
Mark Olson's user avatar
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16 votes

Why is Mars cold?

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 ...
pela's user avatar
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16 votes
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Which is brighter, Mars as seen from Earth, or Earth as seen from Mars?

At it's brightest, Earth is a rather impressive magnitude -2.5 when viewed from Mars1 (the maximum brightness depends on how favourable the elongation is, but it isn't usually brighter than -2) At the ...
James K's user avatar
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15 votes
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When was the martian dichotomy first observed?

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 ...
Stuart Robbins's user avatar
15 votes
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How new is this crater?

To directly answer your questions before providing context: It takes "awhile" for brightness differences of ejecta to disappear on Mars, but unlike the Moon where it's around ~1 billion ...
Stuart Robbins's user avatar
14 votes
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How did ancient astronomers know to order the planets from the closest to the farthest from the Sun?

According to the Cambridge Concise History of Astronomy (p 33 of my edition), essentially the Greeks took the (not unreasonable) view that the planets that moved more slowly were further away and were ...
adrianmcmenamin's user avatar
14 votes
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What explains the distribution of new impact craters on Mars?

I was on the targeting team for one of the cameras that discovered most of these new impact craters. The reason for the distribution is simply because it's easiest to find "new" impact craters in the ...
tanyaofmars's user avatar
14 votes
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Are Tharsis Montes and Hellas Basin a result of the same event?

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 ...
David Hammen's user avatar
  • 34.1k
14 votes
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When was the last volcanic eruption on Mars?

Berman and Hartman (2002) dated some lava flows of the Athabasca–Marte Valles system at < 20 Ma (mega-annum). Later, Vaucher et al. (2009) dated lava flows of the same region, finding ages even ...
Jean-Marie Prival's user avatar
14 votes

How could Mars' atmosphere be shed by solar winds, when Venus has a thick atmosphere despite no magnetic field?

One of the main loss mechanisms of atmospheres escape is thermal escape (Jeans escape) into space. The average thermal velocity at a given temperature $T$ for a molecule of mass $m$ is $$ v_{th} = \...
planetmaker's user avatar
  • 19.6k
13 votes

Are there lightning bolts on Mars?

Lightning Detected on Mars, 2006 With those dust storms, it's difficult to believe that you would not get sufficient charge separation. At only a few hectopascal pressure, thunder might be hard to ...
Wayfaring Stranger's user avatar
13 votes

Salinity of Martian water 3.5 Billion years ago

The article "Water Activity and the Challenge for Life on Early Mars" finds that the early Martian ocean would have been acidic and almost as salty as the dead sea. The estimates for ...
James K's user avatar
  • 123k
12 votes
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Does Mars contain more iron than the Earth?

Mars definitely has far less Iron than Earth. Mars has 10.7% of Earth's mass. On the other hand, Iron comprises 32% of Earth since there is so much Iron in its inner core, outer core, and the mantle. ...
RichS's user avatar
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12 votes
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Strange square-like formation on Mars

I looked at the image and annotated it based on what it most likely is: In black is the formation itself. In blue is a depression underneath it. In grey is part of the boundary of what you believed ...
HDE 226868's user avatar
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12 votes
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Are there Earth rocks on Mars?

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 ...
Natsfan's user avatar
  • 4,494
12 votes

On Mars, why are the seasons "strongly amplified" in the southern hemisphere and masked in the northern hemisphere?

Apart from the eccentricity you pointed out that has a role in a difference in the weather, one more factors that plays a role is the difference in the terrain and topology between the hemisphere. ...
Nilay Ghosh's user avatar
  • 4,477
11 votes
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Why are Mars northern/southern hemisphere altitudes so different?

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 ...
usernumber's user avatar
  • 17.5k
11 votes
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Which is closer to the Earth, Phobos, Deimos or Mars?

To expand on fasterthanlight's excellent answer: on average, Mars is the closest. The reasoning behind this claim perhaps is best illustrated with a (not to scale) picture showing that Mars and a ...
Connor Garcia's user avatar
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