| The Hertzsprung-Russell (HR) diagram is one of the most important diagrams in astronomy.
In a HR diagram, the luminosity of stars and/or stellar remnants (white dwarf stars, WD’s),
relative to the luminosity of the sun, is plotted versus their surface temperatures (Teff). The
Earth shows a striking similarity in size (radius ≈ 6.370 km) and Teff of its outer core
surface (Teff ≈ 3800 K at the core-mantle-boundary) with old WD’s (radius ≈ 6.300 km)
like WD0346+246 (Teff ≈ 3820 K after ≈ 12.7 Ga [1]), which plot in the HR diagram close
to the low-mass extension of the stellar population or main sequence. In the light
of nuclear planetology [2], Earth-like planets are regarded as old, down-cooled
and differentiated black dwarfs (Fe-C BLD’s) after massive decompression, the
most important nuclear reactions involved being 56Fe(γ,α)52Cr (etc.), possibly
responsible for extreme terrestrial glaciations events (“snowball” Earth), together
with (γ,n), (γ,p) and fusion reactions like 12C(α,γ)16O. The latter reaction might
have caused oxidation of the planet from inside out. Nuclear planetology is a new
research field, tightly constrained by a coupled 187Re-232Th-238U systematics. By
means of nuclear/quantum physics and taking the theory of relativity into account, it
aims at understanding the thermal and chemical evolution of Fe-C BLD’s after
gravitational contraction (e.g. Mercury) or Fermi-pressure controlled collapse (e.g.
Earth) events after massive decompression, leading possibly to an r-process event,
towards the end of their cooling period [2]. So far and based upon 187Re-232Th-238U
nuclear geochronometry, the Fe-C BLD hypothesis can successfully explain the
global terrestrial MORB 232Th/238U signature [3]. Thus, it may help to elucidate
the DM (depleted mantle), EMI (enriched mantle 1), EMII (enriched mantle 2) or
HIMU (high U/Pb) reservoirs, and the 187Os/188Os isotopic dichotomy in Archean
magmatic rocks and sediments [4]. Here I present a conceptual model constraining the
evolution of a rocky planet like Earth or Mercury from a stellar precursor of the
oldest population to a Fe-C BLD, shifting through different spectral classes in a HR
diagram after massive decompression and tremendous energy losses. In the light of
WD/BLD cosmochronology [1], solar system bodies like Earth, Mercury and Moon are
regarded as captured interlopers from the Galactic bulge, Earth and Moon possibly
representing remnants of an old binary system. Such a preliminary scenario is supported
by similar ages obtained from WD’s for the Galactic halo [1] and, independently,
by means of 187Re-232Th-238U nuclear geochronometry [2, 4, 5], together with
recent observations extremely metal-poor stars from the cosmic dawn in the bulge of
the Milky Way [6]. This might be further elucidated in the near future by Th/U
cosmochronometry based upon a nuclear production ratio Th/U = 0.96 [5] and
additionally by means of a newly developed nucleogeochronometric age dating
method for stellar spectroscopy, which will be presented in a forthcoming paper. The
model shall stimulate geochemical data interpretation from a different perspective to
constrain the (thermal) evolution of a habitable planet as to its geo-, bio-, hydro- and
atmosphere.
[1] Fontaine et al. (2001), Public. Astron. Soc. of the Pacific 113, 409-435. [2] Roller
(2015), Abstract T34B-0407, AGU Spring Meeting 2015. [3] Arevalo et al. (2010), Chem.
Geol. 271, 70-85. [4] Roller (2015), Geophys. Res. Abstr. 17, EGU2015-2399. [5] Roller
(2015), 78th Annu. Meeting Met. Soc., Abstract #5041. [6] Howes et al. (2015), Nature 527,
484-487. |