Hot answers tagged

68

The biggest advantage of Mars is there are resources available on that planet. Run out of oxygen? Make your own! Same with water. Set up refining, and you can make your own metal. Large windows are more difficult in no atmosphere than Mars's thin atmosphere, which makes growing crops easier, at least according to The Case for Mars. I believe this is because ...


41

The big problem is that space is empty. To build the space station, people need to haul every single gram there. Every single atom on a space station needs to be shipped there at cost--whether it's from an asteroid, planet, or elsewhere. On Mars you have the ability to use local resources. You can easily dig and build using the resources at hand without ...


28

There is Carnot's theorem for the theoretical maximum efficiency of heat engines. It is valid not only for mechanical engines like steam engines or Stirling engines but also for solid state devices like the thermocouples used in RTGs. The Carnot efficiency depends on the upper and lower working temperature. $$ \eta = 1 - \frac {T_c}{T_h} $$ Tc is the cold ...


26

Radiation I think this is actually the biggest concern, IMO. Astronauts aboard the ISS have a measurably increased risk of cancer due to their higher radiation exposure. Putting enough shielding on a space hab to reduce risk to earth surface levels would be unimaginably expensive. On the other hand, Mars has gigatons of surface rock which makes a pretty ...


23

The thing your're missing is that the Hohmann Transfer orbit takes time, and both Mars and Earth are moving around the sun. For the Hohmann Transfer orbit to work, the position of Mars at arrival has to be opposite the point of of Earth at Departure. The following image depicts Earth's and Mars' orbit as circular, rather than elliptical to simplify ...


12

All heat engines, whether mechanical or solid state, produce work based on heat flow across a temperature difference. The maximum efficiency of a heat engine depends on how large that difference is.


8

The highest resolution images come from the HiRISE camera on the Mars Reconnaissance Orbiter. With an angular resolution of one micro-radian it has a ground resolution of about 0.3 m (12 inches) Here's an image of the Phoenix lander on its parachute, at a resolution of about 30cm taken from https://static.uahirise.org/images/2008/details/cut/...


7

Solar Irradiance Mars has seasons, just like Earth. While Mars weather is significantly less interesting than Earth's, due to the thinner atmosphere, the average temperature difference between summer and winter can be more than 50 C. The difference between daytime high and low can be more than 120 C. If we consider the three forms of heat transfer, we can ...


6

HiRise routinely observes at high latitudes. In fact I can quickly find these examples: At $86.8^\circ$: https://hirise.lpl.arizona.edu/ESP_035295_2670 At $82.2^\circ$: https://www.uahirise.org/ESP_027324_2625 At $87.9^\circ$: https://www.uahirise.org/PSP_010623_2680 At $85.8^\circ$: https://www.uahirise.org/PSP_010636_2660 You have a large gallery of high ...


6

No, Perseverance will not drive for months with the helicopter stowed on its underside. From the Surface Phase of the Mars 2020 Perseverance Launch Press Kit I got the information below. The first 30 sols after landing will be a commissioning phase within which the rover will perform a short drive test. After that Perseverance will need to find a flat area ...


6

Are there other good reasons to choose Mars instead of space stations in some orbit? Perhaps the following non-technical but social argument could be a good reason: Much like in the space-race to the Moon, exploring natural solar bodies with actual humans can have profound and inspiring effects on (both/all) colonies of conscious beings. Having a spaceship, ...


5

I found this article for the 2012 Curiosity rover launch which stated that NASA Television will be broadcasting live coverage of Curiosity's landing on Aug. 5 beginning at 8 p.m. EDT (I also found this video showing the mission control room during the landing but I don't know if that was shown live) So, I suppose that it is probable that we will see live ...


5

There were some instruments attached to the heatshield that took measurements of the atmosphere during the entry, descent, and landing phase. This suite was referred to as MEDLI (MSL EDL Instruments). This was used for gathering data about how the heatshields performed, and what the atmosphere around them was like, during EDL. While instruments measuring how ...


4

Answering the "what would work?" part of the question: I would use an electret haired brush which barely touches the surface of the solar panels. Electret filters are very effective in collecting fine particles. The brush is mounted on a simple wiper. Once it collected the brown powder it vibrates downstream to shed the dust of, a bit like a dog ...


4

Other answers have already mentioned the availability of resources and the ability to endure disasters, which I agree are two key reasons. I have not yet seen anyone mention what I consider the third key reason. Elon Musk does not just want to take us to Mars, he wants to make humanity a multiplanetary species. Sufficiently many people (a commonly ...


4

Is Perseverance still in Safe Mode? Not any more: NASA's Mars rover Perseverance is fine and out of 'safe mode' as of July 31, 2020.


3

It was as of the latest update, but they were working on recovering it. They have full communication with the spacecraft as of now. The press release, issued on July 30, stated the following: Right now, the Mars 2020 mission is completing a full health assessment on the spacecraft and is working to return the spacecraft to a nominal configuration for its ...


3

The 3 vacuum engines will be used for Trans Mars Injection (TMI) since they are more efficient in vacuum. While each one is off centered, firing all 3 will make it balanced, so this makes the most sense. For landing, it will be a bit trickier. I haven't seen anything publicly, but I suspect they will use the vacuum engines for part of the time, and the 3 sea ...


3

Partial answer; rather than an areostationary orbit with zero inclination, an inclined areosynchronous orbit (i.e. same period but tilted) would never lose direct line-of-sight to Earth except when it goes behind the Sun. From the surface of Mars it would make a figure-eight in the sky once a day (see this answer for what those look like), but these days ...


3

Much of engineering is about compromises. One can find an ideal solution, like a Hohmann transfer orbit. Yes, that is the most fuel efficient way to get from earth orbit to Mars orbit. It is like the top of a rounded mountain. That is the peak, but there is a lot of ground near the peak that is almost as high. Maybe you are willing to give up a bit of ...


3

It's motivational. Had JFK given us a more realistic goal than landing a man on the moon by the end of the decade, we would have failed. Such a goal might have been: First, I believe that this nation should commit itself to achieving the goal, before this decade is out, of establishing a permanent outpost in space, in preparation for landing a man on our ...


3

There is a giant committee set up among all the space powers to coordinate this. From the ESA page: http://www.esa.int/esapub/bulletin/bulletin121/bul121e_marelli.pdf "The Space Frequency Coordination Group (SFCG): The SFCG was created 24 years ago as an ESA and NASA initiative. It is an informal group composed of frequency managers from all of the ...


2

It's a bit of a late answer, but most proposals don't actually use increased CO2 to warm up the planet. They use super-greenhouse gases (like perfluorocarbons), or they increase the amount of sunlight hitting Mars. As for a terraforming roadmap, there's one by Robert Zubrin, which proposes that it would take about a thousand years. However, others argue ...


2

Actually, it's possible to use perfluorocarbons to create the necessary greenhouse effect: https://science.nasa.gov/science-news/science-at-nasa/2001/ast09feb_1. These are much stronger greenhouse gases than CO2 and are also non-toxic. Of course, terraforming would still be an expensive and long-term project, even using these gases.


2

I think the reasons are psychological - that occupying and building a life on a planet is more comprehensible and appeals better to people, by using the appearance of opportunities that are in a more familiar form. It is easier to popularise and market than promoting the building of space habitats. Any colony attempts will rely heavily on taxpayer funded ...


2

Resources, as Pearson mentioned, are the key; specifically matter. An object in the inner Solar System is emphatically not a closed system, so the second law of thermodynamics does not apply: Any object here is embedded in the Sun's radiation, an inexhaustible source of low-entropy energy. This energy flux enables it to lower its entropy (by radiating even ...


2

@JamesK's answer indicates that HiRise is the "highest resolution camera on a Mars orbiter" but it's worth noting that it is also (at least currently) the highest resolution known, human-built camera anywhere in deep space! @Phiteros' answer to What's the largest aperture telescope sent beyond the Earth-Moon system? begins: After looking through ...


1

Many sources. (eg this one) mention the samples orbiting Mars in a "basketball-sized" container until collected by the Earth Return Orbiter. I haven't seen any authoritative ones saying it's also shaped like a basketball.


1

Quite possibly Upon learning that Mars did have surface water at some point, you have updated your question to ask if Mars would be a good approximation for Earth if Earth had little to no water, or if the water had been missing for a period of time. Conversely, try looking at areas of the Earth that have had little to no water, or where the water has been ...


1

Why will we go to Mars? It certainly is not ideal to build a colony on Mars. There are many threats to human life there - it is one of the deadliest environments a human could be in. To Elon Musk, inspiration is the key to human progress and motivation - we will go to Mars for the same reason that humans do space exploration at all - it inspires us and we ...


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