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This press release is copyright Nature.
VOL.460 NO.7256 DATED 06 AUGUST 2009
This press release contains:
· Summaries of newsworthy papers:
Planetary science: Martian methane hard to explain
Astronomy: Unravelling an enigma
Virology: HIV architecture on display
Astronomy: Galaxy evolution a massive mystery
And finally… Economic boost, fertility bust?
· Mention of papers to be published at the same time with the same embargo
· Geographical listing of authors
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[1] Planetary science: Martian methane hard to explain (pp 720-723)
The patterns of methane observed on Mars are hard to fathom using current atmospheric chemistry or physics, a Nature paper suggests.
Recent observations suggest spatial and temporal variations of methane on Mars. But methane has a photochemical lifetime of several centuries and so is expected to have a spatially uniform distribution on the planet. Franck Lefèvre and François Forget use a global climate model of Mars with coupled chemistry to simulate the Martian methane cycle. They find that methane chemistry, as currently understood, does not predict measurable variations on the planet.
In order to reproduce local methane enhancements similar to those recently reported, an unidentified methane loss process that is 600 times faster than predicted by standard photochemistry is necessary, which is difficult to reconcile with the observed distribution of other trace gas species on Mars. Destruction of methane on the surface of Mars would have to occur within about one hour to explain the recent observations. If observations of spatial and temporal variations of methane are confirmed, this would suggest an extraordinarily harsh environment for the survival of organics on the planet.
CONTACT
Franck Lefèvre (Université Pierre et Marie Curie, Paris, France)
Tel: +33 1 44 27 47 73; E-mail: [email protected]
[2] Astronomy: Unravelling an enigma (pp 701-704)
Cosmic rays travel almost at the speed of light and rain down on Earth continuously, but the origins of some of them are still somewhat of a mystery. Recent studies have suggested that some of these rays may come from the shock waves associated with supernovae — giant, exploding stars. A review article in Nature this week argues that astronomers may in fact be on the wrong track altogether in looking for isolated regions of acceleration from supernovae.
Made up of protons, other ions and electrons, Galactic cosmic rays are high-energy charged particles that enter the solar system from the outside. Their paths are often scrambled by the magnetic fields of planets so that even if detected, it is nearly impossible to determine their origin.
Yousaf Butt outlines the problems associated with the supernova theory, suggesting that the scenario is oversimplified, and even if a strong signature from a supernova were to be found, it would not be sufficient to prove that they are the main accelerators of Galactic cosmic rays. He proposes that more general models are needed to come up with a holistic picture of how cosmic rays gain energy.
CONTACT
Yousaf Butt (Harvard-Smithsonian Center of Astrophysics, Cambridge, MA, USA)
Tel: +1 617 953 5108; E-mail: [email protected]
[3] Virology: HIV architecture on display (pp 711-716; N&V)
The structure of the entire HIV-1 genome is revealed in this week’s Nature, shedding new light on the regulatory relationship between RNA structure and function and on the AIDS-causing virus.
HIV-1, like many other viruses, carries its genetic information as RNA rather than DNA, folded into distinct ‘secondary’ structures. Kevin Weeks and colleagues used a high-throughput RNA analysis technology called SHAPE to decode the genome structure of the virus at the single nucleotide level. As expected, the composition of nucleotides influences protein production, but the team also show that protein translation and folding are influenced by these structural elements within the RNA. This suggests that RNA structure may have a previously unappreciated role in the expression of the genetic code.
The analysis also highlights many highly structured motifs in the HIV-1 genome, where previously only a handful had been described in any detail. It’s thought that these characteristic RNA patterns probably have regulatory roles.
CONTACT
Kevin Weeks (University of North Carolina, Chapel Hill, NC, USA)
Tel: +1 919 962 7486; E-mail: [email protected]
Hashim Al-Hashimi (The University of Michigan, Ann Arbor, MI, USA) N&V author
Tel: +1 734 615 3361; E-mail: [email protected]
[4] Astronomy: Galaxy evolution a massive mystery (pp 717-719; N&V)
In an observational tour de force, astronomers have made a new measurement to support recent suggestions that the most massive galaxies in the early Universe were much smaller and more dense than their counterparts today. This leaves theorists with the challenge of explaining how today’s galaxies evolved.
Recent observations of very distant massive galaxies — galaxies so far away that their light left them more than 10 billion years ago — caused a stir by suggesting that they were about five times smaller than similar galaxies are today, while seeming to contain about the same number of stars. Theoretical models of galaxy evolution were unable to explain how today’s galaxies could have evolved from their more compact predecessors — unless the masses of the early galaxies, which were inferred from their colours and luminosities, had been overestimated. An increase in size accompanied by an increase in mass would be easy to explain by mergers between galaxies.
In this week’s Nature, Pieter van Dokkum and colleagues argue against the easy explanation, with an independent measurement of the mass of one of the compact early galaxies. The measurement, based on the orbital velocities of the galaxy’s stars, as revealed by the broadening of absorption lines in the galaxy’s spectrum, supports the earlier mass estimate, putting the ball squarely back in the theorists’ court.
CONTACT
Pieter van Dokkum (Yale University, New Haven, CT, USA)
Tel: +1 203 432 3019; E-mail: [email protected]
Karl Glazebrook (Swinburne University of Technology, Melbourne, Australia) N&V author
Tel: +61 3 9214 4384; E-mail: [email protected]
[5] And finally… Economic boost, fertility bust? (pp 741-743; N&V)
In the 20th century, an increase of wealth in developed nations has been accompanied with a decline in human fertility to rates below population replacement. But, this negative trend reverses itself once a certain degree of economic development is reached, as reported online in this week’s Nature.
The increase in global ageing population and the decrease in birth rates has lead to socioeconomic concerns with regards to issues such as workforce maintenance. Many developed, or developing, countries have feared that the population decrease would become irreplaceable.
Hans-Peter Kohler and colleagues, however, have found a ‘J’-shaped correlation between economic development and fertility, which indicates that a reversal is possible. They looked at total fertility rate and the human development index (HDI) in 24 countries over a 30-year time span. At low and medium HDI levels there was fertility decline, but when HDI reaches advanced levels, such as it is now in the United States and the Netherlands, fertility decline reverses and slowly begins to rise.
CONTACT
Hans-Peter Kohler (University of Pennsylvania, Philadelphia, PA, USA)
Tel: +1 215 898 7686; E-mail: [email protected]
Shripad Tuljapurkar (Stanford University, CA, USA) N&V author
Tel: +1 650 724 4171; E-mail: [email protected]
ALSO IN THIS ISSUE…
[6] Observation of strong coupling between a micromechanical resonator and an optical cavity field (pp 724-727)
[7] Fluid and deformation regime of an advancing subduction system at Marlborough, New Zealand (pp 733-736)
ADVANCE ONLINE PUBLICATION
***These papers will be published electronically on Nature's website on 05 August at 1800 London time / 1300 US Eastern time (which is also when the embargo lifts) as part of our AOP (ahead of print) programme. Although we have included them on this release to avoid multiple mailings they will not appear in print on 06 August, but at a later date. ***
[8] Developmental and species-divergent globin switching are driven by BCL11A
DOI: 10.1038/nature08243
[9] L1 Retrotransposition in Human Neural Progenitor Cells
DOI: 10.1038/nature08248
GEOGRAPHICAL LISTING OF AUTHORS…
The following list of places refers to the whereabouts of authors on the papers numbered in this release. For example, London: 4 - this means that on paper number four, there will be at least one author affiliated to an institute or company in London. The listing may be for an author's main affiliation, or for a place where they are working temporarily. Please see the PDF of the paper for full details.
AUSTRALIA
Melbourne: 8
AUSTRIA
Innsbruck: 6
Vienna: 6
FRANCE
Paris: 1
ITALY
Milan: 5
JAPAN
Nagoya: 8
Tokyo: 7
NETHERLANDS
Leiden: 4
NEW ZEALAND
Wellington: 7
SPAIN
Granada: 9
UNITED STATES OF AMERICA
California
La Jolla: 9
San Diego: 7
Connecticut
New Haven: 4
Maryland
Chevy Chase: 9
Frederick: 3
Massachusetts
Boston: 8
Cambridge: 2
Michigan
Ann Arbor: 9
New Jersey
Princeton: 4
North Carolina
Chapel Hill: 3
Pennsylvania
Philadelphia: 5
Texas
Austin: 8
Utah
Salt Lake City: 7
Washington
Seattle: 8
PRESS CONTACTS…
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Tel: +1 202 737 2355; E-mail: [email protected]
From Japan, Korea, China, Singapore and Taiwan
Mika Nakano, Nature Tokyo
Tel: +81 3 3267 8751; E-mail: [email protected]
From the UK/Europe/other countries not listed above
Jen Middleton, Nature London
Tel: +44 20 7843 4502; E-mail [email protected]
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