# What If We Had More Iron?

Back home, 84% of Earth's core is iron, one of the most abundant elements in the cosmos. We have used it for many purposes in the 6,000 years of human history, from the heads of arrows and spears to the core of any steel alloy.

But what if Earth's core had more iron, along the lines of 90%?

How would it affect the planet's relationship with our moon? How would it affect the magnetic field? Would it have affected the size of the planet in any way? If not, then would it have affected the history of civilization?

• Well I mean, I highly doubt our ancestors were embarking on journeys to the core of the earth to gather molten iron for their spears ;) At any rate, I can't see it having a huge effect on civilization. It would probably make for a denser core and maybe a slightly increased gravity, but without doing the math that's pure speculation. Dec 29, 2015 at 20:59
• The answer is, as always, it depends. Where will this iron come from, and will it add to or replace other elements in the core? Which ones? Or will we just remove the other elements until we're at 90% iron and call it good? Add some more details as to what exactly you're imagining is happening and I'll be happy to write you an answer. Dec 29, 2015 at 21:08
• Iron has only been significant for about 3000 years. Prior to the was the Bronze Age. Dec 30, 2015 at 4:45
• Then expect more rust... Dec 30, 2015 at 8:01
• Only tangentially relevant, but maybe useful for you if looking to understand the role of iron in a planet's overall composition: iron planet and banded iron formation. Mar 26, 2017 at 22:04

Planet mass isn't significantly affected; as explained above, other layers are mostly unaffected, while core is made of Iron with Nickel on distant second. Iron has density of $7.8 \frac{g}{cm^3}$, Nickel has density of $8.9 \frac{g}{cm^3}$. Assuming that 1/3 of mass is contained in core (result of quick google search), by replacing 6% of its mass with Iron you are decreasing planet's mass by $0.3(3)*6\%*\frac{7.8}{8.9}\approx 1.7\%$ dropping planet's gravity to $9.64 \frac{m}{s^2}$ compared to real Earth's $9.81 \frac{m}{s^2}$. Sorry, here I made a mistake in previous version you are decreasing mass, not increasing as I previously wrote.