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This questions may seem naive, but, worth pondering:

As humans keep sending more and more missions to space (outside earth's system), the earth is being affected in the following ways:

  1. Earth is losing mass (though negligible, yet cumulative). The point to consider is that most space missions do not return physical matter back to earth and luckily we do not get hit by meteors, asteroids or comets; thus the matter lost may not be replenished.
  2. Space missions send out hard to find or extract, precious minerals/metals/fuel. Even if space debris falls to earth, mere rock is not the same as metals and other elements.

So the question, if we keep sending out space missions, will earth be impacted negatively?

Update: Many have pointed out that most missions end up in debris that falls back on Earth. I wish to place on record, that I am specifically pointing at non-LEO missions, such as the deep impact probe, Mars missions, Pluto missions etc., specifically in the future, when such missions will increase in frequency.

anurag
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    For an order of magnitude estimation, check this: https://qntm.org/destroy What it would take to use up Earth's mass: "At a million tonnes of mass driven out of the Earth's gravity well per second, this would take 189,000,000 years." – vsz Jan 25 '23 at 05:52
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    "luckily we do not get hit by meteors, asteroids, or comets" - but Earth does get hit by something on the order of thousands of tons of dust per year. – Cadence Jan 25 '23 at 06:35
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    @Cadence, but does that dust replenish the Gold, Platinum, Titanium, etc that we are sending out? – anurag Jan 25 '23 at 11:29
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    What do you consider a negative effect? IF someone used Viking space magic to strip the entire top ten kilometers off the surface of the Earth and hurl that into interstellar space, the solar system wouldn't change, the Earth and moon's orbit wouldn't be noticeably different. The biosphere and oceans would basically be destroyed, but Earth itself would continue trucking along. – notovny Jan 25 '23 at 11:39
  • does that dust replenish the Gold, Platinum, Titanium, etc that we are sending out - partially, but way more of those materials end up useless in landfills than we ever send to space. We mine those minerals because there are concentrations, but most of it is in the core. In all of human history we've only mined about enough gold to cover a 100m square area 1.5ft thick, the gold in the core is enough to coat the entire planet. In 2026 we'll see if 16 Psyche really is a planetesimal with $10 quadrillion (1000 times the world GDP) in precious metals. – Jason Goemaat Jan 26 '23 at 05:58
  • @Cadence In fact, "Multiple geochemical studies have concluded that asteroids are most likely the primary source of Earth's water." – Peter - Reinstate Monica Jan 26 '23 at 14:50
  • Re "most space missions do not return physical matter back to earth": What makes you think that? To the contrary, all spacecraft in Earth orbits will eventually return because even space is not free of friction (admittedly, it will take a long time for spacecraft in geosynchronous orbits). – Peter - Reinstate Monica Jan 26 '23 at 14:56
  • Mandatory almost-xkcd: https://www.nytimes.com/2019/12/10/science/earth-size-mass.html – Peter - Reinstate Monica Jan 26 '23 at 15:02
  • Also, consider the 50,000 tons of mass loss every year, mostly in the form of gaseous hydrogen diffusing into space (the kinetic energy of some molecules/atoms is larger than the negative energy in the gravity well). I bet you that during solar storms the solar wind carries a lot more of the upper atmosphere away. – Peter - Reinstate Monica Jan 26 '23 at 15:06

4 Answers4

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With increased space exploration missions, are we affecting earth's mass?

In theory, yes. In practice, no. The amount of mass we send into space is completely negligible compared to the huge mass of the Earth. Besides, most of that mass comes crashing back down onto the Earth. The vast majority of spacecraft sent into space are placed into low Earth orbit. By international agreement, that stuff is supposed to deorbit within 25 years. The amount of material we have sent into geosynchronous orbit is tiny. The amount of material we have sent beyond Earth's orbit is tinier than tiny. But it is there, which is why I wrote "in theory, yes."

David Hammen
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    It would be interesting to compare the mass lost due to launches with the mass gain due to meteorites and meteoritic dust. – JohnHoltz Jan 25 '23 at 03:27
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    But do we lose metals? because most LEO crafts burn up upon re-entry - forming oxides and scattered in atmoshpere - hard to recover. Also, aren't rocket fuels hard to make? Is there any recorded data by some watchdog regarding loss/gain of earth's mass? – anurag Jan 25 '23 at 04:31
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    Plenty of processes on Earth "waste" metals by converting them to oxides. I'm sure iron is lost from ships in vast quantities over the years due to rusting and much of that ends up in the oceans. Iron is not in short supply. Being concerned about loss of metals due to rocket launches would be a little like an ant worrying about sand grains being lost from a mountain range. Rocket fuels come in a range of types some are hard to make, but many are not. Kerosine, methane and liquid oxygen are not hard to make. There is no watchdog it's simply an insignificant non-issue. – Slarty Jan 25 '23 at 07:48
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    ...it's simply an insignificant non-issue..., for now, I would add! – anurag Jan 25 '23 at 11:27
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    People used to think the same thing about mining petroleum, landfills, flushing waste into oceans, etc. – Barmar Jan 25 '23 at 16:12
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    @Barmar if we ever utilize space so much that the loss becomes anywhere near noticeable, I'd file that under "good problems to have", because it implies that we're finding some kind of resource off-planet to make all that launching worthwhile. – hobbs Jan 26 '23 at 02:25
  • (or at least humanity has contnued to exist as a technological civilization for far longer than currently seems likely) – hobbs Jan 26 '23 at 02:27
  • @Barmar When humanity must start worrying about the mass it puts into space at a planetary scale it's a sign that we have reached the stage of a Kardashev type 1 civilization: We will harness most of the energy that reaches our planet, and proceed to harness the rest of the Sun's output. (ctd.) – Peter - Reinstate Monica Jan 26 '23 at 15:15
  • ... Kardashev was concerned with energy, not mass, but mass is a necessary corollary: In order to harness energy on a planetary level, you must physically alter the planet; in order to harness energy on a stellar level, you must physically alter the star system (harvest planetoids or entire planets). – Peter - Reinstate Monica Jan 26 '23 at 15:15
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The earth gains about 43 tons of mass every day in meteorites and space dust. We are not only not decreasing the mass of the earth with our space program but are not even keeping it from growing.

John Meacham
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    Your answer could be improved with additional supporting information. Please [edit] to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers in the help center. – Community Jan 25 '23 at 06:47
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    Next question for https://skeptics.stackexchange.com : "Is it true that the Earth gains 43 tons of mass every day in meteorites and space dust?" – Stef Jan 25 '23 at 09:09
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    There is also a reduction due to atmosphere being blown away, but the mass of arriving material is probably more interesting – GremlinWranger Jan 25 '23 at 09:35
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    @stef see https://earthscience.stackexchange.com/questions/16688/is-earth-getting-heavier-or-lighter also a potential source of sources for this answer – GremlinWranger Jan 25 '23 at 09:38
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    @GremlinWranger Awesome, thanks! Although the accepted answer to that question says "After all additional effects are balanced, the Earth looses about 50,000 tons a year.", so pretty much the opposite of what this answer says. – Stef Jan 25 '23 at 15:01
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    Estimates for how much mass is gained via meteorites and space dust versus how much is lost by gas escape vary all over the place, by multiple orders of magnitude. – David Hammen Jan 25 '23 at 16:18
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The mass of Earth is $5.97\times10^{21}$ tons. The launch mass of SpaceX's Starship (the upper stage, with payload and fuel) is roughly 1200 tons. Even if we sent a Starship to orbit to orbit each hour since the launch of Sputnik (October 4, 1957, 7:28pm), we would only have launched 687,000,000 tons so far. This is 0.000,000,000,01% of the total mass of Earth.

This mass so negligible that the effect of it on the elemental composition of Earth is literally zero by all practical means. For example, one of the rarest stable elements, tantalum, averages to an abundance of 2ppm. Even if all the launched mass in the above scenario was pure tantalum, we would still have 99.999995% of what we had initially.

And mind that most of this mass would eventually fall back to Earth anyway.

It's safe to say we're safe.

Russell Borogove
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Neinstein
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From your comments I glean that, even if most spacecraft return to Earth in a timely fashion, you are still concerned about the loss of precious resources due to scattering.

I'd like to put this in the context of the bigger picture: The scattering of precious resources is inherent to all human activity. All activity in a closed system increases entropy. We mine concentrated ores, do something with it, and eventually it's ending up in the environment because try as you might: All recycling is "leaky".

Earth, thank goodness, is not a closed system: It is basking in the low-entropy energy flow from the Sun, which is the reason we can exist: Organisms are precious islands of low entropy which depend on a steady flow of energy through them. Because of this energy flow (and some nuclear energy) we can revert some of the scattering: Filter water and air, recycle garbage etc.

But in the great scheme of all human activity, spaceflight is only peripheral, and the mass flow through satellites is more or less irrelevant. So much metal is elsewhere dispersed in the environment through oxidation and dissolution. Just think about the billion or so rusting cars on the streets and in the junkyards, or ships rusting in salt water.

Apparently, the total amount of mass sent into orbit, ever, is about 14,933,443 kg, or 14,933 metric tons.

What are the numbers for cars? The yearly number of cars produced is about 80,000,000, weighing about 1.4 metric tons each. That's 112,000,000 tons of steel per year, or 12,700 per hour.

More steel is mined, refined, processed and assembled for cars in two hours than the entire mass put into orbit by mankind, ever. 24/7, 365 days a year.

Sure, a significant fraction of that is recycled, but a significant fraction is simply rusting away in some scrapyard.

Peter - Reinstate Monica
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