Comments on: Our prehistoric ancestors got iron-ey https://habitablezone.com/2016/08/23/our-prehistoric-ancestors-got-iron-ey/ Sat, 25 Apr 2026 16:17:27 -0700 hourly 1 http://wordpress.org/?v=3.3.1 By: ER https://habitablezone.com/2016/08/23/our-prehistoric-ancestors-got-iron-ey/#comment-37316 ER Wed, 24 Aug 2016 04:28:30 +0000 https://www.habitablezone.com/?p=59331#comment-37316 All elements lighter than iron are formed by the fusion of lighter nuclei in stellar interiors. They can be returned to the interstellar medium by planetary nebula (a temporary outgassing phase of old, sunlike stars) or by supernovae of more massive stars). Heavier elements are formed by neutron absorption during supernova events, and returned to the IM. So all elements (except the hydrogen)in the earth's crust are from dead stars, and those heavier than iron are from supernovae. Since the earth formed from the primordial nebula 4.6 Gyr ago, iron deposits dated by their isotopic abundance to just a few million years of age must have come from a much more recent event, certainly not from the original solar nebula. Either a supernova event occurred nearby, or the solar system recently plowed the debris of such an event in its orbit around the galaxy. There are several known supernova remnants within a few thousand light years of us, perhaps one of them is the culprit. It makes you wonder what other interesting events are a part of our planet's history, and how many of them left evidence that could be used to place them in our timeline. I wouldn't be a bit surprised if tectonic activity hasn't erased the traces of much older episodes in our planet's past...another good reason to go to other, less disturbed bodies in our solar system, and to look there for that evidence. All elements lighter than iron are formed by the fusion of lighter nuclei in stellar interiors. They can be returned to the interstellar medium by planetary nebula (a temporary outgassing phase of old, sunlike stars) or by supernovae of more massive stars). Heavier elements are formed by neutron absorption during supernova events, and returned to the IM. So all elements (except the hydrogen)in the earth’s crust are from dead stars, and those heavier than iron are from supernovae.

Since the earth formed from the primordial nebula 4.6 Gyr ago, iron deposits dated by their isotopic abundance to just a few million years
of age must have come from a much more recent event, certainly not from the original solar nebula. Either a supernova event occurred nearby, or the solar system recently plowed the debris of such an event in its orbit around the galaxy. There are several known supernova remnants within a few thousand light years of us, perhaps one of them is the culprit.

It makes you wonder what other interesting events are a part of our planet’s history, and how many of them left evidence that could be used to place them in our timeline.

I wouldn’t be a bit surprised if tectonic activity hasn’t erased the traces of much older episodes in our planet’s past…another good reason to go to other, less disturbed bodies in our solar system, and to look there for that evidence.

]]>