Prof.
Devendra Lal
(14
February, 1929 - 01 December, 2012)
Life and Science of
Prof. Devendra Lal
Prof. Devendra Lal, an illustrious cosmic ray physicist, earth and planetary
scientist and distinguished mentor passed away on 1st December, 2012
at his residence in San Diego, California. He was 83. Prof. Lal was a Fellow of
the Physical Research Laboratory, Ahmedabad (India) and a Professor at the
Scripps Institution of Oceanography, San Diego, California (USA). He belonged
to the generation of scientists who commanded a wide range of scientific
interests; his research spanned diverse areas of Earth and Planetary Sciences,
from the Earth's mantle to the Moon and beyond. The novel ideas, approaches and
experimental methods conceived and developed by Prof. Lal jointly with his
students and colleagues to pursue studies in Earth and Planetary Sciences, and
the seminal and innovative contributions that ensued from them ushered new
knowledge and led to major strides in our understanding of basic processes
operating in various planetary reservoirs.
Prof. Lal, joined the Tata
Institute of Fundamental Research, Mumbai in 1949, after completing his Masters
in Physics from the Banaras Hindu University (BHU), a move that laid the
foundation for his prolific research career. Even as a young student of physics
at BHU, he had a natural fascination for chemistry that continued throughout his
scientific career. Indeed it is this fascination, as Prof. Lal has occasionally
reminisced, that prompted him while he was a student to make fireworks,
vanishing creams and fountain pen ink and market them locally at Banaras. It is
also such adventures of Prof. Lal in chemistry combined with his extraordinary
drive and never say 'impossible' attitude that led to new analytical approaches
in his studies of Earth and Planetary Sciences; a classic example being the use
of iron hydroxide impregnated sponges and fibers for in-situ extraction of
adequate quantities of extremely low abundant radioactive isotopes and trace
elements from tons of sea water for their application in nuclear oceanography.
In recent years Prof. Lal was
keenly interested to adapt such methods or develop newer ones for cost
effective purification of ground waters from toxic metals such as arsenic. The
strong link between physics and chemistry in Prof. Lal's research made Prof. J.
R. Arnold, a long term friend and colleague of Prof. Lal at the University of
California, San Diego, to describe Prof. Lal on the occasion of his election as
a Foreign Associate of the US National Academy of Sciences as 'For a physicist, the best chemist there is'.
Prof. Lal's early research at
the Tata Institute of Fundamental Research with Profs. H. J. Taylor and
B.Peters on the properties of cosmic rays led to the characterization of the
nature of elementary particles and their interactions much before the dawn of
high energy accelerator era. It was around this time that Prof. W.Libby and his
colleagues announced the discovery of radiocarbon (14C) produced in
the atmosphere by the interaction of cosmic rays with atmospheric nitrogen and
its potential applications in Earth Sciences. Prof. Peters and Lal recognizing
the importance of this discovery coupled with the realization that cosmic ray
interactions with atmospheric constituents would also produce a suite of other
radionuclides, long lived 10Be in particular, that can serve as
tracers to investigate Earth surface processes shifted their research focus to
the estimation of production rates of cosmogenic nuclides in the atmosphere and
exploit their applications in Earth Sciences. This resulted in a series of
pioneering and bench mark publications that opened a completely new field of
research on cosmogenic nuclides in earth surface reservoirs and their
applications. The widely different chemical and nuclear properties of these
nuclides make them unique and ideally suited to investigate a variety of basic
processes, e.g. circulation, scavenging and precipitation in the atmosphere and
oceans, and sedimentation on the ocean floor details of which were brought out
in the classic publications of Lal and Peters during 50's and 60's. On the
personal front, it was also during the early 1950's that Prof. Lal courted his
colleague Ms. Aruna and married her in 1955. Mrs. Aruna Lal, had been the
pillar of strength and support for Prof. Lal's research career and
achievements.
The scope of Prof. Lal's
research considerably widened during the 60's to include topics on prehistory
of cosmic rays and planetary evolution based on in-depth studies of signatures
of cosmic rays in meteorites. This was a natural extension of his earlier work
on cosmogenic nuclides in earth surface reservoirs. Prof. Lal and colleagues
retrieved for the first time the paleointensity of cosmic rays in the galaxy
through measurements of cosmogenic nuclides in meteorites, a study that
established the potential of such records to determine the exposure history of
meteorites in space.
Their subsequent in-depth
studies of signatures of cosmic ray interactions with matter stored in
meteorites and lunar samples provided new knowledge on several Planetary, Solar
System and Astrophysical processes; these include the composition and energy
spectrum of heavy iron group particles (Z >22) in galactic cosmic rays
during the past, the exposure history of lunar grains to solar flare particles,
and lunar regolith dynamics at the Apollo and Luna landing sites.
The lunar research programme
of Prof. Lal and colleagues at TIFR and later at PRL followed their earlier
discovery of individual solar flare irradiated grains in gas rich meteorites
which led them to predict and look for records of solar cosmic ray irradiation
in samples from the Moon as it is devoid of an atmosphere. These studies
underscored the great value of lunar samples to investigate processes which
occur during exposure of materials to solar radiation in space.
In 1972 Prof. Lal made a
major career move, he shifted to the Physical Research Laboratory (
The discovery of several
cosmic ray produced isotopes (e.g.32Si, 28Mg, 38S,
38Cl, 34mCl) in the early 60's by Prof. Lal and his
colleagues at TIFR and Scripps and studies on their distribution in the
stratosphere and troposphere yielded details of large scale atmospheric
circulation and quantitative data on time scales for the removal of
contaminants introduced into the atmosphere, e.g., fission products from
nuclear weapon tests and chemical pollutants from industries. In addition to
atmospheric sciences, Prof. Lal also made major advances on the applications of
these isotopes as tracers to investigate the hydrology of oceans and
sub-surface waters, specifically on the determination of "ages" of
water masses and their movement and nutrient dynamics in the sea. These
applications became an integral part of major international oceanographic
programmes such as the GEOSECS designed to track deep water movements and their
rates. These investigations led Prof. Lal and his group to probe in greater
detail particle dynamics in the ocean and to explore the use of biogenic opal
in marine sediments to retrieve past records of surface ocean biogeochemistry
and climate change.
The development
of Accelerator Mass Spectrometry to measure extremely low concentrations of
long lived cosmogenic isotopes in environmental samples formed the basis for
Prof. Lal to conceive and establish another new and major area of cosmogenic
nuclide applications based on in-situ
produced isotopes, particularly 10Be and 26Al to study
the exposure history of rock (glacier) surfaces. This new application extended
the utility of cosmogenic nuclides to studies from the atmosphere to the
surface of the Earth.
Prof. Lal's contributions
to this field through theoretical estimation of nuclide production rates in
exposed surfaces and novel experimental approaches to measure their extremely
low concentrations opened an avenue for obtaining quantitative estimates of
erosion rates and exposure ages of rocks for which reliable data were not
available. This approach is used extensively by earth scientists as it places
geomorphologic studies, which has direct relevance to global rock cycles and
regional tectonics, on a quantitative footing for the first time.
The sad demise
of Mrs. Aruna Lal in 1993 devastated Prof. Lal. The professional achievements
of Prof. Lal were in no small measure due to Mrs. Aruna Lal's sustained
emotional and intellectual support. During her later years she was keen to
support and promote children's education in and around Ahmedabad. Prof. Lal
established the Aruna Lal Trust, administered through
The hallmark of Prof. Lal's
research has been his wholesome approach of combining both theoretical and
experimental studies to exploit nuclear interactions to probe planetary
physical and chemical processes and to determine their time scales. Prof. Lal's
seminal work on the calculations of nuclide production rates resulting from
cosmic ray interactions with various Earth reservoirs and other solar system
objects and their validation through innovative experiments laid the foundation
and subsequent development of the field of "Cosmogenic Nuclide
Applications in Earth and Planetary Sciences". Prof. Lal strongly advocated
an interdisciplinary approach to scientific investigations and the wide
spectrum of his activities bear ample testimony to this as they combine inputs
from the fields of cosmic rays, nuclear physics, earth and planetary sciences
and astrophysics.
Prof. Lal believed and
promoted development of human resource as a part of his research and also
looked for societal relevance in his programs. He established the first
National Radiocarbon Laboratory at TIFR, an important goal of which was to
determine the chronology of ancient cultures of India to learn about the march
of civilization in this part of the globe. The work carried out at this
facility led to building a robust chronology of ancient civilizations in India
which demonstrated that various cultures co-existed during different periods.
Prof. Lal's studies in hydrology and particle dynamics and water circulation in
the oceans have direct relevance to ground water recharge and movement and
contaminant transport in the sea that are topics of societal importance.
Prof. Lal, has been actively
involved in promoting science education, particularly in the field of Earth and
Planetary Sciences. He has mentored a large number of students for their
Masters and Doctoral research both in India and USA; four generations of
students have benefited from his tutelage, many of whom continue to pursue a
research career and contribute to the global school in Earth and Planetary
Sciences.
Prof. Lal's research
contributions have won him several national and international recognitions. He
is a Fellow of the Royal Society (1979), Foreign Associate of the National
Academy of Sciences, USA (1975), Founder Fellow of the Third World Academy of
Sciences, Fellow of the American Association for the Advancement of Science and
Fellow of all the three science Academies in India. He is a recipient of the
several awards that include Bhatnagar Prize (1967), Goldschmidt Award (1997)
and Sir C.V. Raman Birth Centenary Award
(1996-1997). Prof.Lal is also a recipient of the civilian award "Padmashri" bestowed by the Government of India.
Prof. Lal has occupied
important positions in several International Scientific Organizations; these
include President of the International Union
of Geodesy and Geophysics (IUGG) during 1983-1987 and the President of
the International Association for Physical
Sciences of the Ocean (IAPSO) during 1979‑83.
Prof.
Lal has more than 200 publications in scientific journals, and about 100
publications in books, encyclopedia and conference proceedings.
In his death all of us have lost a versatile and distinguished
colleague, an illustrious Earth and Planetary Scientist, a great teacher and
mentor whose life and work will be an inspiration for the new generation of
scientists to pursue high quality research and take forward the reverberations
of his inquisitive mind and his intellectual and child like curiosity.
See
Also: Scripps
News
December,
2012