Oral histories in meteoritics and planetary science—XXIV: William K. Hartmann

In this interview, William Hartmann (Bill, Fig.  1 ) describes how he was inspired as a teenager by a map of the Moon in an encyclopedia and by the paintings by Chesley Bonestell. Through the amateur journal “Strolling Astronomer,” he shared his interests with other teenagers who became lifelong colleagues. At college, he participated in Project Moonwatch, observing early artificial satellites. In graduate school, under Gerard Kuiper, Bill discovered Mare Orientale and other large concentric lunar basin structures. In the 1960s and 1970s, he used crater densities to study surface ages and erosive/depositional effects, predicted the approximately 3.6 Gyr ages of the lunar maria before the Apollo samples, discovered the intense pre‐mare lunar bombardment, deduced the youthful Martian volcanism as part of the Mariner 9 team, and proposed (with Don Davis) the giant impact model for lunar origin. In 1972, he helped found (what is now) the Planetary Science Institute. From the late 1970s to early 1990s, Bill worked mostly with Dale Cruikshank and Dave Tholen at Mauna Kea Observatory, helping to break down the Victorian paradigm that separated comets and asteroids, and determining the approximately 4% albedo of comet nuclei. Most recently, Bill has worked with the imaging teams for several additional Mars missions. He has written three college textbooks and, since the 1970s, after painting illustrations for his textbooks, has devoted part of his time to painting, having had several exhibitions. He has also published two novels. Bill Hartmann won the 2010 Barringer Award for impact studies and the first Carl Sagan Award for outreach in 1997.

Figure 1 Open in figure viewer PowerPoint William K. Hartmann taken 2010 Aug 2 (Photo: Gayle Hartmann).

DS

Bill thank you very much for doing this. I would like to start with a very general question. What is the one incident in your life above all others that has determined the nature of your career?

WKH

I would say that what initially stirred my excitement for this topic were the books I stumbled across as a teenager. One event I recall was that my brother, who was 8 years older than I was, had a young person's encyclopedia called the Book of Knowledge. One day I was looking at that book and there was this map of the Moon. Craters, mountains, plains, all sorts of features. That blew me away. The concept that there was this other land, not just a shining thing in the sky, but a geological body, a new geographical place. There was also a book by Willy Ley and Chesley Bonestell, Conquest of Space, which had all these marvelous paintings by Bonestell, visualizing what it was like on other planets. It came out in 1949. I am fond of my copy of that book because my father somehow managed to get Willy Ley, a German expatriate colleague of von Braun's, a writer and popularizer for space, to come to our town and give a talk and autograph my book. Many years later I met Chesley Bonestell and got him to autograph the book. There are not very many copies of that book with the signatures of both authors! The paintings gave me a real desire to want to know what it would be like on other worlds.

     

ROY—A multiscale magnetospheric mission

The scientific rationale of the ROY multi-satellite mission addresses multiscale investigations of plasma processes in the key magnetospheric regions with strong plasma gradients, turbulence and magnetic field annihilation in the range from electron inertial length to MHD scales.The main scientific aims of ROY mission include explorations of:

(a)

turbulence on a non-uniform background as a keystone for transport processes;

(b)

structures and jets in plasma flows associated with anomalously large concentration of kinetic energy; their impact on the energy balance and boundary formation;

(c)

transport barriers: plasma separation and mixing, Alfvenic collapse of magnetic field lines and turbulent dissipation of kinetic energy;

(d)

self-organized versus forced reconnection of magnetic field lines;

(e)

collisionless shocks, plasma discontinuities and associated particle acceleration processes.

In the case of autonomous operation, 4 mobile spacecrafts of about 200 kg mass with 60 kg payload equipped with electro-reactive plasma engines will provide 3D measurements at the scales of 100-10000 km and simultaneous 1D measurements at the scales 10-1000 km. The latter smaller scales will be scanned with the use of radio-tomography (phase-shift density measurements within the cone composed of 1 emitting and 3 receiving spacecrafts).We also discuss different opportunities for extra measurement points inside the ROY mission for simultaneous measurements at up to 3 scales for the common international fleet.Combined influence of intermittent turbulence and reconnection on the geomagnetic tail and on the nonlinear dynamics of boundary layers will be explored in situ with fast techniques including particle devices under development, providing plasma moments down to 30 ms resolution.We propose different options for joint measurements in conjunction with the SCOPE and other missions:

•

simultaneous sampling of low- and high-latitudes magnetopause, bow shock and geomagnetic tail at the same local time;

•

tracing of magnetosheath streamlines from the bow shock to near-Earth geomagnetic tail;

•

passing “through” the SCOPE on the inbound orbit leg;

•

common measurements (with SCOPE and other equatorial spacecraft) at distances of ∼ few thousand km for durations of ∼several hours per orbit.

The orbit options and scientific payload of possible common interest are discussed in this work, including FREGAT cargo opportunities for extra payload launching and the “Swarm” campaigns with ejection of nano- and pico-satellites.     

Three types of liquid water in icy surfaces of celestial bodies

It is shown that, at temperatures far below the triple point and under appropriate conditions, liquid water can stably or temporarily exist in upper ice-covered surfaces of planetary bodies (like Mars) in three different types:

(i)

undercooled interfacial water (due to freezing point depression by van der Waals forces and “premelting”),

(ii)

water in brines (due to freezing point depression in solutions), and

(iii)

sub-surface melt water (due to a solid-state greenhouse effect driven heating).

The physics behind and the related conditions for these liquid waters to evolve and to exist, and possibly related consequences, are discussed. These calculations are mainly made in view of the possible presence of these sub-surface liquids in the upper surface of the present Mars.     

Scientific field training for human planetary exploration

Forthcoming human planetary exploration will require increased scientific return (both in real time and post-mission), longer surface stays, greater geographical coverage, longer and more frequent EVAs, and more operational complexities than during the Apollo missions. As such, there is a need to shift the nature of astronauts’ scientific capabilities to something akin to an experienced terrestrial field scientist. To achieve this aim, the authors present a case that astronaut training should include an Apollo-style curriculum based on traditional field school experiences, as well as full immersion in field science programs. Herein we propose four Learning Design Principles (LDPs) focused on optimizing astronaut learning in field science settings. The LDPs are as follows:

(1)

LDP#1: Provide multiple experiences: varied field science activities will hone astronauts’ abilities to adapt to novel scientific opportunities

(2)

LDP#2: Focus on the learner: fostering intrinsic motivation will orient astronauts towards continuous informal learning and a quest for mastery

(3)

LDP#3: Provide a relevant experience—the field site: field sites that share features with future planetary missions will increase the likelihood that astronauts will successfully transfer learning

(4)

LDP#4: Provide a social learning experience—the field science team and their activities: ensuring the field team includes members of varying levels of experience engaged in opportunities for discourse and joint problem solving will facilitate astronauts’ abilities to think and perform like a field scientist.

The proposed training program focuses on the intellectual and technical aspects of field science, as well as the cognitive manner in which field scientists experience, observe and synthesize their environment. The goal of the latter is to help astronauts develop the thought patterns and mechanics of an effective field scientist, thereby providing a broader base of experience and expertise than could be achieved from field school alone. This will enhance their ability to execute, explore and adapt as in-field situations require.     

Hydrogen collisions in planetary atmospheres, ionospheres, and magnetospheres

Hydrogen is the most abundant element in the universe. Molecular hydrogen is the dominant chemical species in the atmospheres of the giant planets. Because of their low masses, neutral and ionized hydrogen atoms are the dominant species in the high atmospheres of many planets. Finally, protons are the principal heavy component of the solar wind.Here we present a critical evaluation of the current state of understanding of the chemical reaction rates and collision cross sections for several important hydrogen collision processes in planetary atmospheres, ionospheres, and magnetospheres. Accurate ab initio quantum theory will play an important role. The collision processes are grouped as follows:

(a)

H⁺+H charge transfer,

(b)

H⁺+H₂(v) charge transfer and vibrational relaxation, and

(c)

H₂(v,J)+H₂ vibrational, rotational, and ortho-para relaxation.

In each case we provide explicit representations as tabulations or compact formulas. Particularly important conclusions are that H⁺+H₂(v) collisions are more likely to result in vibrational relaxation than charge transfer and H₂ ortho-para conversion is at least an order-of-magnitude faster than previously assumed.     

Upgrading of some instrumentation devoted to increase space radiation environment understanding

Three methods permitting to characterize space and onboard spacecraft radiation environment have been developed and/or upgraded in our laboratories: MDU equipment with a semiconductor detector as sensitive element devoted to register energy deposition spectra in the Si-diode; a spectrometer of the linear energy transfer (LET) based on chemically etched polyallyldiglycolcarbonate (PADC) track etch detectors (TED); and thermoluminescent detectors (TLDs) with different dependences of relative TL yield on the LET of particles transferring their energy in them.We have used all these types of dosimetry equipments onboard spacecrafts since several years and succeeded to treat directly read data in terms of both quantitative and qualitative dosimetry characteristics and deduce from them related radiation risk.During last few years all these three types of detectors have been intensely studied to understand still better their possibilities to characterize space radiation fields. Particularly:

1.

Both PADC TED LET spectrometer and TLDs have been exposed in heavier ion beams with LET in water ranging from 1 to about 700 keV/μm with the goal to upgrade their calibration curves;

2.

A new method of MDU directly read data has been developed, permitting to measure not only dose in Si-detector, but also to estimate radiation protection quantities and the neutron contribution to the onboard exposure level;

3.

All three methods have been tested onboard spacecrafts during several missions.

Contribution presents, analyses and discusses the results obtained in items 1-3 and, also, the possibilities of these detectors to help in characterizing radiation fields during longer space missions, above 1 year.     

Thermokarst processes and the origin of crater-rim gullies in Utopia and western Elysium Planitia

We have identified a number of gullies that could be aqueous in origin near or at the rim of several impact craters in Utopia Planitia and western Elysium Planitia (30.0°-59.0° N; 241.0°-291.0° W). Based on the sharpness of their incisions and the general absence of superposed craters, we ascribe a relatively recent origin to the gullies. Scalloped depressions are commonplace throughout the region, as well as on the crater walls, rims and floors near the areas of gully issuance. Occasionally, the depressions cross-cut the gully debris-aprons, suggesting that the formation of some depressions is even more recent than that of the gullies. Previous research has proposed that the depressions are collapse basins formed by thermokarst processes. On Earth, thermokarst landforms occur in areas of low gradient topography where the permanently frozen ground (permafrost) is ice rich and has undergone a change in thermal equilibrium. This change can be triggered by long-term or episodic/cyclic climate change and accompanying rises in mean temperatures towards ∼0 °C as well as by rises in seasonally sustained summer temperatures well above ∼0 °C. In order to explain the origin of the rim or near-rim gullies we invoke high obliquity and the possibility that this region of Mars experienced obliquity-driven rises in temperature, atmospheric pressure and humidity sufficient to keep surface water and near-surface ground-ice stable for extended periods of time. We propose that gully formation is closely related to local freeze-thaw processes that, in turn, generate a thermokarst landscape (of which the gullies are a part). This geological and climatological scenario comprises the following steps:

1.

An inundation of meltwater at high obliquity (due to the thawing of an atmospherically-deposited snowpack or ice-sheet) and the subsequent saturation of the underlying regolith to tens of metres of depth.

2.

Loss of water on the surface, perhaps as obliquity decreases slightly, followed by the progressive freezing of the saturated regolith; this creates an aggrading mass of ice-rich regolith.

3.

Obliquity-induced temperature rises that engender the thaw, drainage and partial evaporation of the near-surface, ice-rich regolith.

4.

Localised formation of thermokarst collapse-basins (alases), as water is evacuated from these basins.

5.

Formation of gullies near, or at, some impact-crater rims as the result of meltwater migration from nearby alases through the thawed regolith to the areas of gully issuance.

Although the plains' materials in this region are in part very old (possibly Hesperian or even Noachian), the mantling deposits and their deformation by thermokarst processes appears to be relatively young. This suggests that recent climatic conditions could have been episodically warmer and wetter than had been previously thought.     

Oral Histories in Meteoritics and Planetary Science – XV: John Wood

Abstract– John Wood ( Fig. 1 ) was trained in Geology at Virginia Tech and M.I.T. To fulfill a minor subject requirement at M.I.T., he studied astronomy at Harvard, taking courses with Fred Whipple and others. Disappointed at how little was known in the 1950s about the origin of the earth, he seized an opportunity to study a set of thin sections of stony meteorites, on the understanding that these might shed light on the topic. This study became his Ph.D. thesis. He recognized that chondrites form a metamorphic sequence, and that idea proved surprisingly hard to sell. After brief service in the Army and a year at Cambridge University, John served for 3 years as a research associate with Ed Anders at the University of Chicago. He then returned to the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, where he spent the remainder of his career. At Chicago, he investigated the formation of the Widmanstätten structure, and found that the process informs us of the cooling rates of iron meteorites. Back in Cambridge, he collaborated with W. R. Van Schmus on a chondrite classification that incorporates metamorphic grade, and published on metal grains in chondrites, before becoming absorbed by preparations for the return of lunar samples by the Apollo astronauts. His group’s work on Apollo samples helped to establish the character of the lunar crust, and the need for a magma ocean to form it. Wood served as President of the Meteoritical Society in 1971–72 and received the Leonard Medal in 1978.

Figure 1 Open in figure viewer PowerPoint John Wood.     

Oral Histories in Meteoritics and Planetary Science – XVII: Joseph Goldstein

Abstract– In this interview, Joseph Goldstein ( Fig. 1 ) recounts how he became interested in meteorites during his graduate studies working with Robert Ogilvie at MIT. By matching the Ni profiles observed across taenite fields in the Widmanstätten structure of iron meteorites with profiles he computed numerically he was able to determine cooling rates as the meteorites cooled through 650–400 °C. Upon graduating, he worked with a team of meteorite researchers led by Lou Walter at Goddard Space Flight Center where for 4 years he attempted to understand metallographic structures by reproducing them in the laboratory. Preferring an academic environment, Joe accepted a faculty position in the rapidly expanding metallurgy department at Lehigh University where he was responsible for their new electron microprobe. He soon became involved in studying the metal from lunar soils and identifying the metallic component from its characteristic iron and nickel compositions. Over the next two decades he refined these studies of Ni diffusion in iron meteorites, particularly the effect of phosphorus in the process, which resulted in superior Fe‐Ni‐P phase diagrams and improved cooling rates for the iron meteorites. After a period as vice president for research at Lehigh, in 1993 he moved to the University of Massachusetts to serve as dean of engineering, but during these administrative appointments Joe produced a steady stream of scientific results. Joe has served as Councilor, Treasurer, Vice President, and President of the Meteoritical Society. He received the Leonard Medal in 2005, the Sorby Award in 1999, and the Dumcumb Award for in 2008.

Figure 1 Open in figure viewer PowerPoint Joseph Goldstein.     

A taxonomic survey of comet composition 1985-2004 using CCD spectroscopy

A summary is presented of our spectroscopic survey of comets extending for roughly 19 years from 1985 to 2004 comprising data for 92 comets of which 50 showed good emissions. All data were re-analyzed using consistent reduction techniques. Our observations of comets over several apparitions and comets observed over an extended period indicate no major changes in compositional classification. To our regret, no major unidentified cometary features were found in our surveyed spectral region of 5200-10400 Å. Absolute production rates for the dominant parent molecule H₂O and the daughter species C₂, NH₂ and CN are determined within the limits of the Haser model as are values for the dust continuum, Afρ. From these data, production rate ratios are calculated for C₂/H₂O, NH₂/H₂O, CN/H₂O and Afρ/H₂O. Excluding the odd Comets Yanaka (1988r), 43P/Wolf-Harrington and 19P/Borrelly, with unusual spectra, our set of comets exhibited relatively uniform composition. Detailed analyses of our data resulted in four taxonomic classes:

-

Comets of typical composition (∼70%); exhibiting typical ratios with respect to water of C₂, NH₂, and CN.

-

Tempel 1 type (∼22%); having a deficiency in C₂ but normal NH₂ abundance.

-

G-Z type (∼6%); having both low C₂ and NH₂ ratios.

-

The unusual object Yanaka (1988r) (∼2%?); no detectable C₂ or CN emission but normal NH₂.

It is uncertain whether there is a clear separation between the comets of typical composition and those with C₂ depletion, or whether the latter consists of a group showing a continuum of decreasing C₂/CN ratios. Our spectroscopic investigations result in a visual record of the various compositional classes, which are illustrated in a number of figures. Production rate comparisons with the comet photometry program of Schleicher and A'Hearn [A'Hearn, M.F., and 4 colleagues, 1995. Icarus 118, 223-270] for 13 comets in common yielded good agreement once the different scale lengths are taken into account. An investigation into the possible origin of our compositional groups with respect to dynamical families of comets shows that the Halley family exhibits essentially no C₂ depletion. These objects were presumably formed in the region of Saturn and Uranus and scattered into the Oort cloud. Comets formed in the space near Neptune, responsible for the scattered Kuiper Belt show a mixture of “typical” and C₂ depleted objects, while we associate comets formed in-situ in the classical Kuiper belt with our C₂ depleted group.     

Spectropolarimetric Observations of Solar Noise Storms at Low Frequencies

A new high-resolution radio spectropolarimeter instrument operating in the frequency range of 15?–?85 MHz has recently been commissioned at the Radio Astronomy Field Station of the Indian Institute of Astrophysics at Gauribidanur, 100 km north of Bangalore, India. We describe the design and construction of this instrument. We present observations of a solar radio noise storm associated with Active Region (AR) 12567 in the frequency range of \({\approx}\,15\,\mbox{--}\,85~\mbox{MHz}\) during 18 and 19 July 2016, observed using this instrument in the meridian-transit mode. This is the first report that we are aware of in which both the burst and continuum properties are derived simultaneously. Spectral indices and degree of polarization of both the continuum radiation and bursts are estimated. It is found that

1. i)
   Type I storm bursts have a spectral index of \({\approx}\,{+}3.5\),
    
2. ii)
   the spectral index of the background continuum is \({\approx}\,{+}2.9\),
    
3. iii)
   the transition frequency between Type I and Type III storms occurs at \({\approx}\,55~\mbox{MHz}\),
    
4. iv)
   Type III bursts have an average spectral index of \({\approx}\,{-}2.7\),
    
5. v)
   the spectral index of the Type III continuum is \({\approx}\,{-}1.6\), and
    
6. vi)
   the degree of circular polarization of all Type I (Type III) bursts is \({\approx}\,90\%\) (\(30\%\)).
    

The results obtained here indicate that the continuum emission is due to bursts occurring in rapid succession. We find that the derived parameters for Type I bursts are consistent with suprathermal electron acceleration theory and those of Type III favor fundamental plasma emission.

     

The effect of a relative infinity on cosmological redshifts

We present anon-general relativistic cosmological model with the following features.

All cosmological objects appear to be receding from each other. There are two mathematically distinct types of objects.

Type I objects have apparent magnitudes and apparent angular diameters comparable to those for standard FLRW models. Their redshifts are bounded; this bound is at least 3.

Type II objects can have unlimited redshifts. They appear significantly smaller than Type I objects with the same redshift, and (for redshifts greater than 1) appear brighter (and more so for larger redshifts).

The model is an extension of classical de Sitter spacetime in which the location of infinity is allowed to be relative.