Hot answers tagged

93 votes
Accepted

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 ...
user avatar
  • 10.4k
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 ...
user avatar
  • 1,498
34 votes
Accepted

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 ...
user avatar
30 votes
Accepted

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 ...
user avatar
  • 1,536
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. ...
user avatar
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 ...
user avatar
  • 611
24 votes
Accepted

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. ...
user avatar
  • 91k
23 votes
Accepted

How did Mars come to have a 24 hour 39 minute day?

"It's believed that the Earth was rotating about once every 5 hours before the theorized collision with a Mars sized coorbiting object referred to as Theia." Almost. Theia did not have to be co-...
user avatar
  • 1,060
23 votes
Accepted

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 ...
user avatar
  • 33.8k
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 ...
user avatar
  • 2,831
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 ...
user avatar
  • 33.8k
15 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 ...
user avatar
  • 7,390
15 votes
Accepted

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 ...
user avatar
15 votes
Accepted

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 ...
user avatar
14 votes
Accepted

Sunsets: Mars/Earth

tl;dr: On Earth, atmospheric molecules scatter blue light more than red. In contrast, on Mars atmospheric, $\mu\mathrm{m}$-sized hematite dust particles happen to give the opposite effect. Scattering ...
user avatar
  • 33.8k
14 votes
Accepted

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 ...
user avatar
13 votes
Accepted

Mars night sky - how many stars visible?

I'll add to Wayfaring Stranger's comments. In fact most of the time you would be able to see fewer stars in the night sky of Mars, than in a good dark night sky on Earth, because of dust obscuration. ...
user avatar
  • 118k
13 votes
Accepted

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 ...
user avatar
13 votes
Accepted

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 ...
user avatar
  • 28.3k
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 ...
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 ...
user avatar
  • 91k
12 votes
Accepted

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 ...
user avatar
  • 34.1k
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. ...
user avatar
  • 3,243
11 votes
Accepted

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. ...
user avatar
  • 752
11 votes
Accepted

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 ...
user avatar
11 votes
Accepted

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 ...
user avatar
  • 16.8k
11 votes
Accepted

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 ...
user avatar
  • 4,336
10 votes
Accepted

What earth organisms might survive if they arrived on Mars?

On the surface of Mars probably none, since it's too dry or too cold, or both, to stay active. Spores or other dormant forms probably could survive for centuries, until radiation will gradually ...
user avatar
  • 11.2k

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