by Kathleen A. Campbella, and Philip Yockb,
aSchool of Environment, University of Auckland, Auckland, New Zealand; bDepartment of Physics, University of Auckland, Auckland, New Zealand
We argue that, even though New Zealand is a small nation, our scientists cannot aim too high nor stretch too far. We should make the most of the special opportunities NZ has to offer, and steer towards new fields or methods of research when opportunities or needs arise. We describe our own efforts over 20 years to pioneer new directions in NZ on an astronomical project named MOA and a geological project on NZ hot-springs. The former project seeks to find habitable planets orbiting stars in the Milky Way. The latter seeks to understand how life arose on planets such as Earth and Mars in the first few billion years following their formation. Both projects attract international support and the participation of our ablest university students.
Keywords: Exploratory science; NZ environment; MOA project; exoplanets; hot spring deposits; life in extreme environments; future prospects
We urge emerging Kiwi scientists, as well as aspiring school leavers, to set their sights high in the choice of field to study, and also to consider fields that specifically make use of New Zealand’s particular geographic and environmental context, following inspiring examples set by our sportspeople, writers and others. Fields such as geothermal energy, extreme life, Antarctic research, marine biology, Polynesian migration, climate science, southern astronomy, phylogeography and biosecurity protecting a unique biota are obvious possibilities, situated as we are astride an active plate tectonic boundary in the Southwest Pacific in the Southern Hemisphere.
We also suggest an exploratory science approach as a recipe for growth and recognition of NZ science by describing two projects that began with the ambitious goal to be globally relevant – i.e., to make a contribution to the advancement of science both within and outside the country – and which made particular use of New Zealand’s special attributes at the frontiers of scientific exploration. Both yielded positive results, and continue to find success.
The first project is known as MOA or “Microlensing Observations in Astrophysics”. It was founded in 1994 as a joint NZ/Japan venture primarily to seek and study planets orbiting stars in the Galaxy that could host life. The second project has been underway amongst a group of geoscientists at the University of Auckland (UOA) since 1996. It focuses on life that is found in “extreme” environments on Earth – particularly heat-loving microbes flourishing in hot springs – and how it finds its way into the fossil record. This research aims to improve our understanding and recognition of early life on Earth (>3 billion years ago) and possibly on Mars.
The MOA Project
Overview of the MOA project.
The MOA project is described in some detail in the September/October 2006 issue of NZ Geographic and at the website http://www.phys.canterbury.ac.nz/moa/.
MOA was formed in 1994 as a collaboration between Japan and New Zealand to utilise a novel technique originally conceived by Einstein (1936) to seek planets orbiting stars in the Galaxy, so-called “exoplanets”, and other difficult-to-find objects. At the time no exoplanets had been detected orbiting stars like the Sun, and the search for them was decidedly unfashionable. Newton and others had speculated that they might exist, but the difficulty of detecting a tiny object like the Earth adjacent to a bright object like the Sun had thwarted all attempts to detect them. Hence was hatched the plan by MOA to use the novel technique of Einstein.
Einstein’s technique utilises his prediction that light does not follow a straight-line path when passing through a gravitational field. Instead it is deviated slightly, rather like a ray of light passing through a glass lens. The deviation causes a distant star to appear both magnified and distorted by the gravitational field of a nearer star (Fig. 1A). The magnification depends on the mass of the lens but not on its luminosity. Dark objects, such as black holes, may therefore be detected.
For Einstein’s lensing effect to be observable, the alignment of the foreground and background stars needs to be very precise. Suitable alignments are rare and temporary, as all stars are in motion. The chance of detecting them is greatest in dense stellar fields near the centre of the Galaxy. These lie in the constellation of Sagittarius which is in the southern sky (Fig. 2). It is for this reason that the MOA project is based in New Zealand (Fig. 1B).As luck would have it, the first detection of an exoplanet was reported in 1995, just one year after the commencement of MOA, by a Swiss group using an entirely different technique. They reported a Jupiter-like planet orbiting a solar-type star at a very small orbital radius, smaller than that of Mercury in our solar system. The Swiss discovery was completely unexpected, and highlighted the ever-present need for observation in science. Since their discovery many “hot Jupiters” have been found. They are quite common.
Results of MOA research.
The first exoplanet found by the gravitational lensing effect was discovered by the MOA group in 2004 (Bond et al. 2004). Confirmatory evidence was found by a Polish group based in Chile. This planet is quite similar to Jupiter but its host star was found to be smaller and cooler (i.e. redder) than the Sun. Since then several Jovian planets have been found orbiting “red-dwarf” stars. Like hot Jupiters, they were unexpected and they are quite common. Smaller planets, not much larger than the Earth (Fig 3B), have also been found using an observational strategy advocated by MOA.
A completely unexpected discovery was reported in 2011. This was of so-called “free-floating” planets (Sumi et al. 2011). These are planet-like objects that appear to roam the Galaxy unattached to stars (Fig. 3A). They are sometimes referred to as “rogue” or “orphan” planets. They outnumber stars in the Galaxy by two to one, but their origin is not understood. The ability of Einstein’s technique to detect dark objects enabled their discovery.
In summary, a novel technique was developed by MOA that yielded original, important and unexpected results. About 40 planets have been found from New Zealand at the time of writing. The research made specific use of our location on the globe. When the project was started the goal was considered to be almost fanciful, but it is now one of the fastest growing fields in astronomy (Fig. 3B). Several students from New Zealand, Japan, France and elsewhere enjoyed their first exposure to research working on the project (Fig. 3C). Amateur astronomers from New Zealand and South Africa also made significant contributions.
Most of the planets shown Figure 3B are either too hot or too cold to support life as we know it. The next logical step is to hunt for habitable exoplanets. The techniques being by MOA and other groups are constantly being refined and the discovery of warm, habitable, terrestrial planets is just a matter of time. A Korean group is presently installing three large microlensing telescopes in Australia, South Africa and Chile with this aim in mind, and the US has plans for a space telescope named WFIRST.
Finding signs of life on a habitable planet will be the next game-changer. Proposals have been made to hunt for bio-signatures such as oxygen in the atmospheres of warm terrestrial planets. One intriguing plan that is presently under consideration by NASA involves flying a pair of spacecraft in tandem 37,000 km apart, with one housing a telescope and a spectroscope to seek bio-signatures, and the other acting as a starshade to block light from the planet’s host star (Seager 2014).
Another possibility is to hunt for bio-signatures on planets orbiting white dwarf stars (Agol 2011). White dwarfs are long-lived and highly evolved forms of stars that might host planets. They have similar masses to the Sun but are comparable in size to the Earth. It would be a relatively simple task to search for bio-signatures in their atmospheres. A starshade would not be required and the observations could be conducted from the ground. The pristine skies and long nights of Antarctica offer an ideal viewing location and a great opportunity for NZ astronomers.
Life in Extreme Environments
The question as to whether life exists or has existed on other planets or moons is as relevant today as it was in the 1970’s with the launch of the Viking missions to Mars – e.g., July 2014 cover story for National Geographic magazine: “Is Anybody Out There? Life Beyond Earth.” While astronomers scan the skies for exoplanets in “habitable windows”, and fine-tune their spectroscopic instruments to measure atmospheric bio-signature gases from afar, planetary geologists, prebiotic chemists, astrobiologists, microbiologists and others apply a suite of tools on Earth and in the Solar System to probe the origin and nature of life in “extreme” environments, past and present (e.g., articles in the international journal Astrobiology). The goal is to provide boundary conditions around where and when life may have evolved without oxygen on a hotter early Earth, the depth to which subsurface microbial worlds may exist, and whether exoplanets and moons may be habitable (Kashefi and Lovley, 2003). NZ science has contributed to this endeavour in several ways, one example of which is highlighted below.
Hot-springs Research at the University of Auckland
History and highlights.
The Auckland Sinter Programme (ASP) was established in 1996 by UOA geoscientists and was joined by a junior American academic (KAC of this article) in 1997, who arrived fresh from post-doctoral studies at the Exobiology Branch of NASA’s Ames Research Center in California. Sinters are siliceous hot-spring deposits. The aims of the research group were to study how “primitive” life that is adapted to high temperatures is distributed in environmental gradients from 100 °C spring-vent effluent areas to cooler channels and ponds (Fig. 4), and to determine how these specialized prokaryotes become incorporated into the fossil record (Fig. 5). Because hot springs in New Zealand, Yellowstone and Iceland are typically mineralizing – trapping the affiliated biota in silica, carbonate or iron discharging from the springs themselves – they therefore provide a ready tomb in which life may be preserved and protected for thousands to millions and potentially even billions of years (Farmer 2000).
Terrestrial hot springs today mimic, to at least some degree, the conditions under which early life may have developed on Earth, and potentially Mars (Farmer, 2000). More than 3 billion years ago Mars was warmer and wetter than today, and hosted volcanoes and running water, which on Earth and Mars promote(d) the formation of hot springs (Bock and Goode 1996). Hydrothermal habitats on Earth teem with extreme life (e.g. Handley and Campbell, 2011) – hyperthermophilic microbes – and have done so for at least the past 400 million years on land (Trewin, 1996), and the past 3.2 billion years at hydrothermal vents in the sea (Rasmussen, 2000).Early Earth also was hotter than today. The sea was full of dissolved silica because of a lack of planktonic organisms like today that scoop it up and use it for their shells (Maliva et al. 2005). Thus, Archean Eon (>2.5 billion years ago) oceans of the distant past were warm and able to precipitate silica as a preserving medium for early life forms in a manner not found on Earth today, except in continental hot springs (Maliva et al. 2005).
The further back in time we go to search for fossil bio-signatures and geochemistry to understand the conditions of the origin and evolution of earliest life, the less clear the rock record of life becomes, obscured by the ravages of erosion and subsequent destructive geological events. Even more fraught is the search for past or present life on Mars, as we don’t even know if life ever evolved there, or if we would recognise it if we came upon it. Thus, there is a need to understand how the deep (most primitive) branches of life’s phylogenetic tree – e.g. the “extreme” life of hyperthermophilic microorganisms in hot springs – become fossilised and incorporated into the geological record.
ASP academics, students and collaborators – with specialties in geothermal geology, mineralogy, paleoecology, microbiology, volcanology, sedimentology, and geologic structure and tectonics – spent a decade meticulously analysing the ubiquitous and spectacular hot-springs and their deposits scattered about the countryside between Rotorua and Taupo, North Island (Figs. 4, 5). See http://www.env.auckland.ac.nz/people/ka-campbell for some relevant literature references. The research clarified the fine details of microbes being encrusted with non-crystalline (amorphous) opaline silica and its transformation through various partially crystalline silica mineral phases to stable microcrystalline quartz, the mineralogic state of most of Earth’s earliest microfossils. DNA studies of modern hot-spring microbes also delineated community composition and its preservation at the earliest phases of silicification.Students are especially intrigued by and involved in the research (Fig. 6). ASP’s focus on silicifying hot springs has been complementary to studies of very old fossils of early prokaryotic life that mostly are preferentially preserved in silica (e.g., Knoll, 1985), as well as recent findings on Mars of nearly pure silica deposits inferred as hydrothermal (Ruff et al., 2011). Recently the work has been expanded to include Jurassic (150 million year old), gold-bearing hot-spring deposits in Patagonia, and Archean (3.3 billion year old), hydrothermally influenced marine strata enclosing fossil microbes in South Africa.
Terrestrial hot-spring deposits are now recognised worldwide as paleoenvironmental archives for extreme life, and analogues for early Earth conditions. They are potential indicators of precious metals mineralisation or extractable heat energy at depth. Moreover, they are used as analogues for past habitable settings on Mars. They also may be dated and mapped to indicate geofluid migration in the crust in relation to zones of crustal weakness or shifts in paleo-climate (e.g., Sturchio et al., 1993). Much effort is also being expended by NZ chemists and microbiologists to inventory the geochemistry, community diversity and ecology of the inhabitants of NZ geothermal areas (e.g., Ward, 2013).
Exploratory science can and should be tackled in small countries such as New Zealand, especially when the physical environment lends itself to the burgeoning science. Isolation from large centres of learning can enable new ideas to be developed and nurtured locally. If the science is exciting and globally relevant, international assistance and collaboration will be forthcoming. Antarctica could provide the next exoplanetary vantage point for NZ astronomers, as Mars could be for sample-return missions for NZ geobiologists.
Both authors thank colleagues, students and the Marsden Fund for support. KC acknowledges in particular Pat Browne, Julie Rowland, Bridget Lynne and the National Geographic Society, and PY warmly acknowledges the co-founding members of MOA. Louise Cotterall and Susan Timberlake helped produce the figures for this article.
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