The post states that tungsten "...has a low corrosion rate at elevated temperatures." This is not accurate.<p>Tungsten oxidizes in air beginning around 600°C and as the temperature increases, the tungsten oxide layer scales off, exposing underlying metal to further oxidation. (see, for example, <a href="http://labfus.ciemat.es/AR/2011/C_004/AM_4x.pdf" rel="nofollow">http://labfus.ciemat.es/AR/2011/C_004/AM_4x.pdf</a>)<p>Tungsten is great for high temperature use in vacuum, neutral (the inert gases) or reducing environments (hydrogen, for example). You can use it nearly up to its melting point in those conditions if you aren't too dependent on structural integrity.<p>In oxidizing environments (air, oxygen, water, halogens, silicates, etc.) it fails quite rapidly. Molten rock is replete with chemical species that react with tungsten at elevated temperatures.<p>At 2000°C, the tungsten blanket covering the Co60 heat source would be corroded away, I'll guess, within a week of launch on its journey to the center of the earth.<p>Although it would be incredibly costly, they might have better luck with iridium or rhenium.<p>Nevertheless, a fun mission to think about.