Aggregate dust particles at comet 67P/Churyumov-Gerasimenko

Area of Science:

• Planetary Science
• Cosmochemistry
• Astrophysics

Background:

• Comets preserve pristine dust from the early solar nebula, crucial for understanding Solar System formation.
• Previous studies suggested cometary dust comprised fluffy agglomerates, based on indirect observations and dust similar to chondritic porous interplanetary dust particles.
• Fine-grained aggregate components in cometary dust were altered during collection in prior missions.

Purpose of the Study:

• To investigate the in situ microscopic properties and aggregation structures of dust particles from comet 67P/Churyumov-Gerasimenko.
• To determine if cometary dust exhibits hierarchical aggregation and to compare its properties with interstellar dust.
• To understand the role of dust aggregation in comet formation and dust release mechanisms.

Main Methods:

• In situ measurements of dust particles using advanced instrumentation on a cometary mission.
• Topographic imaging of dust particles ranging from one micrometer to tens of micrometers.
• Analysis of grain morphology, size, and elongation.

Main Results:

• Cometary dust particles from comet 67P/Churyumov-Gerasimenko are aggregates of smaller, elongated grains.
• Hierarchical aggregation structures were observed at distinct size scales.
• Dust particle morphologies varied, including compact single grains and porous aggregates similar to chondritic porous interplanetary dust particles.
• Measured grain elongations align with values inferred for interstellar dust.

Conclusions:

• Cometary dust grains may represent building blocks of comets, originating from interstellar dust.
• Hierarchical agglomeration is a significant process in the growth of cometary dust aggregates.
• The hierarchical structure of dust aggregates influences the tensile strength of the cometary nucleus, facilitating dust release.