Atomic Force Microscopy for Martian Investigations
Author(s)
Sykulska-Lawrence, Hanna Maria
Type
Thesis
Abstract
The Phoenix Mars Lander includes a Microscopy, Electrochemistry and Conductivity
Analyser (MECA) instrument for the study of dust and regolith at
the Martian arctic. The microscopy payload comprises an AFM and Optical
Microscope (OM) to which samples are delivered by a robot arm. The setup
allows imaging of individual dust and soil particles at a higher spatial resolution
than any other in-situ instrument. A fully functioning test-bed of the
flight microscopy setup within an environmental chamber to simulate Mars
conditions was assembled at Imperial College, enabling characterization of
the microscopes.
Samples are collected on small disks rotated to the vertical position for
imaging, with each substrate surface promoting different adhesion mechanisms.
The vertical mounting necessitates good adhesion of particles to
substrates. Moreover, to achieve safe operation and good AFM scans, a
sparse field of particles is required.
This work investigates models and experimental setups which consider
the adhesion mechanisms of particles, including under Mars conditions.
These models incorporate the forces from the AFM cantilever during scanning, particle-substrate adhesion and particle-tip adhesion.
The solution offered to the problem of unstable particles is substrates
with engineered features, micromachined in silicon, to trap and stabilise
particles for AFM and reduce the loading of the sample to a suitable level.
Various designs were investigated in a series of tests, and a final design was
created for a substrate for AFM during the mission. The substrates were
fabricated and incorporated on the sample wheel on Phoenix, now on Mars.
The MECA results are discussed, focusing in particular on the characterization,
calibration and cataloguing of samples using the Imperial College
testbed. The best ways of obtaining data from the setup were investigated.
These strategies were used during the Phoenix mission.
Finally, the extant microscopy data acquired during surface operations
are presented and the overall operations procedures discussed.
Analyser (MECA) instrument for the study of dust and regolith at
the Martian arctic. The microscopy payload comprises an AFM and Optical
Microscope (OM) to which samples are delivered by a robot arm. The setup
allows imaging of individual dust and soil particles at a higher spatial resolution
than any other in-situ instrument. A fully functioning test-bed of the
flight microscopy setup within an environmental chamber to simulate Mars
conditions was assembled at Imperial College, enabling characterization of
the microscopes.
Samples are collected on small disks rotated to the vertical position for
imaging, with each substrate surface promoting different adhesion mechanisms.
The vertical mounting necessitates good adhesion of particles to
substrates. Moreover, to achieve safe operation and good AFM scans, a
sparse field of particles is required.
This work investigates models and experimental setups which consider
the adhesion mechanisms of particles, including under Mars conditions.
These models incorporate the forces from the AFM cantilever during scanning, particle-substrate adhesion and particle-tip adhesion.
The solution offered to the problem of unstable particles is substrates
with engineered features, micromachined in silicon, to trap and stabilise
particles for AFM and reduce the loading of the sample to a suitable level.
Various designs were investigated in a series of tests, and a final design was
created for a substrate for AFM during the mission. The substrates were
fabricated and incorporated on the sample wheel on Phoenix, now on Mars.
The MECA results are discussed, focusing in particular on the characterization,
calibration and cataloguing of samples using the Imperial College
testbed. The best ways of obtaining data from the setup were investigated.
These strategies were used during the Phoenix mission.
Finally, the extant microscopy data acquired during surface operations
are presented and the overall operations procedures discussed.
Date Issued
2008-10
Date Awarded
2009-03
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Pike, William
Sponsor
EPSRC, STP and PPARC (now STFC)
Creator
Sykulska-Lawrence, Hanna Maria
Publisher Department
Electrical and Electronic Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)