Flux and size fractionation of 3He in interplanetary dust from Antarctic ice core samples

Abstract

Accretion of extraterrestrial material to earth is of interest for a variety of reasons, including as a possible driver of long or short-term climate change, and as a record of solar system events preserved in the geological record. hypothesis that helium in IDPs is primarily solar helium implanted in particle surfaces.

A record of the extraterrestrial 3He flux through the Late Cretaceous

“…Only small particles which effectively re-radiate heat, or rare larger particles on unusually low velocity trajectories, arrive on the Earth's surface with their He intact. Modeling suggests that most 3 He-bearing IDPs penetrating the atmosphere are smaller than about 30 lm (Farley et al, 1997), a result confirmed by a few direct measurements (Mukhopadhyay and Farley, 2006;Brook et al, 2009;McGee et al, 2010). While meteorite fragmentation has been proposed as an important source of the extraterrestrial 3 He flux (Lal and Jull, 2005), this possibility has been refuted (Brook et al, 2009).…”

Evaluating the accretion of meteoritic debris and interplanetary dust particles in the GPC-3 sediment core using noble gas and mineralogical tracers

“…(2) noble gas retentivity (as proposed by Mukhopadhyay and Farley (2006)); and (3) presence of grain sizes <10 lm (Mukhopadhyay and Farley, 2006;Brook et al, 2009). Additional, anecdotal evidence includes the presence of dendritic grains consistent with stoichiometric ilmenite and ulvospinels.…”

“…Fukumoto et al, 1986;Hiyagon, 1994). Recent studies suggest >60% of retained 3 He resides in the <37 lm particle fraction, while approximately half is within particles between 5 and 13 lm (Mukhopadhyay and Farley, 2006;Brook et al, 2009).…”

“…Particles 20-25 lm in diameter settle quickly (>100s of meters/day) and uniformly settle to the ocean bottom; however, these particles lost >90% of their He during atmospheric entry (Farley et al, 1997a,b). IDPs 5-10 lm in diameter, which dominate [ 3 He] in ice cores (Brook et al, 2009), settle slowly ($cm/day), although turbulent surface processes and irregular shapes may drastically lower this settling velocity. Thus, aggregation with other debris likely regulates the deposition of these small (<5-10 lm), He-rich particles.…”

What caused terrestrial dust loading and climate downturns between A.D. 533 and 540?

“…A major drawback to most of these tracers is that they require relatively large volumes and stratigraphic thicknesses of ice. For example, a study of extraterrestrial He 3 abundance in replicate samples found that around 1000 g of ice were needed to achieve reproducible results with 2σ errors on the order of ±30% (Brook et al, 2009). Another study achieved lower errors, but individual samples represented over 100 yr of ice accumulation (Winckler and Fischer, 2006).…”