More than just a blueprint for life, DNA is proving to be one of the most versatile materials in nanotechnology.

A DNA molecule is made from 4 building blocks--the chemical bases A, C, G, and T. Nanotechnologists take advantage of the fact that they can obtain DNA strands with any sequence of bases to design strands that bind together to make novel structures. G always binds to C, and A is similarly complementary to T. Researchers at Bell Labs/Lucent Technologies and the University of Oxford have previously constructed short strands of synthetic DNA that bind together to make a simple molecular machine---a pair of molecular tweezers that can be opened and closed by adding additional DNA strands (Yurke et al., Nature, 10 August 2000).

Now, they have made a fuel, consisting of DNA loops, that can act as a source of energy for DNA-based molecular motors. The loops react very slowly unless a specially designed DNA strand is present to catalyze the reaction by forcing loops open. They propose that this principle could be used to make a molecular motor (not yet built). The motor would act as a catalyst,pulling open two complementary DNA loops. The opened loops would bind to each other, exerting a force in the process which could for example cause the motor to rotate or move down a track. The motor would slowly deplete the DNA fuel--and run freely until the fuel was exhausted.

Possible applications of artificial molecular motors include nanoscale conveyor belts that carry molecular cargo in a nanoscale asssembly line.

Curiouser and curiouser and curiouser.

The parallels in this story with the James Ossuary are becoming just a little too bizarre for words. Perhaps there's a divine hand¹ at work here.

Israeli Police Break Ancient Tablet

An ancient stone tablet some experts believe may date to the 9th century B.C., providing rare confirmation of biblical narrative, broke in half while being moved to an Israeli police station, officials said Monday.

An antiquities collector turned in the shoebox-sized tablet in Tel Aviv on Monday morning. Police bringing it to Israel's Antiquities Authority in Jerusalem broke it even though it was wrapped in two layers of bubble wrap and inside a box, said Amir Ganor, the head of the authorities' anti-theft division.

Officials didn't say how the break occurred, but a spokeswoman for the Antiquities Authority, Osnat Guez, said it could actually help scientists studying the tablet, since they will be able to check the inner layers to determine how old the stone is.

[More]

Here's an update on that Jehoash Inscription, a stone tablet found containing a Hebrew inscription that appears to echo key passages from the Book of Kings (also mentioned here).

Antiques collector hands over 'Joash Inscription' to police

The "Joash Inscription", a dark gray sandstone tablet, measuring 1 foot by 2 feet, with 15 lines in ancient Hebrew found some years ago during renovations on Jerusalem's Temple Mount, was transferred to the police fraud squad by antiques collector Oded Golan on Monday.

Golan had been arrested and interrogated over the past few days in connection to the inscription, and has previously denied owning the inscription.

The inscription was located by the police after a six-week undercover investigation, and will be transfered from Tel Aviv to the inspection of the Antiquities Authority in Jerusalem.

The Antiquities Authority will appoint a team of archeologists, geologists and other experts to determine whether the inscription is authentic.

[More]

Curiouser and curiouser...  ¶ 1:33 pm

About 3.6 billion years ago, Mars was a planet covered with oceans. Today, it's one covered with deserts and the only water on the planet is in the form of sub-surface permafrost which melts from time to time. Oceans cannot exist on a planet without an atmosphere (and Mars has only a very thin one) because it is pressure from the atmosphere that stops surface water from instantly vaporising. So the story of the loss of Mars' oceans is intimately connected with the loss of the Martian atmosphere.

One factor to consider is that Mars has a relatively weak gravitational field (Mars' is half the size of Earth) which means that its atmosphere is not as strongly bound to it as the Earth's is but a far more critical factor is that Mars also lacks a strong magnetic field to protect it from solar winds.

Solar winds are high energy streams of charged particles that are emitted in huge quantities by the Sun. Atoms in the upper reaches of a planet's atmosphere get ionised by the Sun's ultra-violet radiation and become susceptible to being blown away with these solar currents. A strong magnetic field is vital for protecting a planet's atmosphere because it serves to deflect solar winds around and away from it. It is thought that even the paltry amount of magnetism that Mars actually does exhibit has been responsible for protecting what little remains of its atmosphere.

So in the a nutshell, the oceans of Mars simply evaporated into space after the atmosphere blew away.

How much water did Mars originally have? It has been estimated that there probably was enough to bathe the entire planet in 30 metres (100 feet) of water. This (conservative) figure was arrived at by observing the relative abundance of different isotopes of hydrogen in the Martian atmosphere and then working backwards.

[Krasnopolsky and Feldman] compared the amount of H2 to the amount of deuterium in the Martian atmosphere, obtained from a 1997 observation by Krasnopolsky using the Hubble Space Telescope. Deuterium is a form of hydrogen made heavier due to the presence of a neutron in its nucleus. Like hydrogen, deuterium can link to an oxygen atom and another hydrogen atom to form water, which in this case is called "heavy water" due to the inclusion of the more massive deuterium atom (HDO).

Both forms of water are broken down by solar ultraviolet radiation and form some quantities of H2 and HD, respectively. H2 and HD rise high in the Martian atmosphere where they may be broken down to their component atoms by chemical reactions. Due to their random thermal (temperature-related) motion, collisions with energetic particles, and chemical reactions, a certain percentage of H and D atoms, and H2 and HD molecules, will have enough velocity to escape the pull of Mars's gravity, so Mars gradually loses its hydrogen and deuterium to space. Hydrogen loss (or deuterium loss) equates to water loss because the atoms are no longer available to recombine and form water in the Martian atmosphere.

Since deuterium is heavier than hydrogen, less deuterium will escape because it takes more energy to get it moving at the necessary speed. By measuring the amounts of deuterium and molecular hydrogen in the Martian atmosphere, the team discovered the degree to which deuterium is preferentially left behind, called the fractionation factor.

Because deuterium is left behind more often, the portion of Martian water that is heavy water rises over time. In fact, earlier measurements revealed that Martian water is 5.5 times richer in heavy water than the water on Earth.

Scientists assume that the Earth and Mars were created with the same initial proportions of heavy water and normal water, called the D to H ratio. If this is correct, once the rate at which deuterium builds up - determined using the fractionation factor - is known, they can work backwards to determine how much additional water would be required to dilute the current Martian water so that its D to H ratio is the same as Earth's.

However, this requires that the current amount of water on Mars be known. Mars is a frigid world, so most of its water is ice. The team used measurements of the volume of the Martian polar caps by the MGS spacecraft for an estimate of the water remaining on Mars today. Additional water may remain frozen in the Martian soil, but this quantity is unknown. However, any water found there only increases the current amount of deuterium-enriched Martian water, which will require an even larger primordial supply to dilute it to an Earth-like level.

The team could calculate backward for as long as the fractionation factor can be applied, which extends to a period about 3.6 billion years ago. Prior to that, the Martian surface was a lot warmer due to heat left over from Mars's formation, and much of the water was in vapor form. This permitted a much greater quantity of water to escape Mars via a different process called hydrodynamic escape.

Other researchers previously determined the D to H ratio for Martian water at the end of the hydrodynamic escape period some 3.6 billion years ago by deriving it from the analysis of the D to H ratio in Martian meteorites. Using the derived ratio for the end of hydrodynamic escape, Krasnopolsky and Feldman calculate that the amount of water required to dilute the D to H ratio in the current Martian water supply so that it matches the D to H ratio of that earlier era is equivalent to a global ocean 100 feet (about 30 meters) deep.

Markings in hardened volcanic ash, dubbed "devils' trails" by local Italian villagers, have been confirmed as the oldest-known footprints ever made by humans.

The fossilised hand and footprints belong to three early humans who were probably climbing down the side of the Roccamonfina volcano in southern Italy about 385,000 to 325,000 years ago, report a team of Italian palaeontologists in today's issue of the journal, Nature.

"We believe that these tracks are the oldest human footprints found so far," said Professor Paolo Mietto of the University of Padua in Italy, who lead the research. "They are made by hominids who had a fully bipedal, free-standing gait, using their hands only to steady themselves on the difficult descent."

"In some of the prints, the impressions made by the heel and ball of the foot are clear, and there are even small depressions that can be interpreted as toe impression," he said.

They were made by primitive humans that walked upright with a free-standing gait and used their hands to steady themselves. Three tracks with prints show curve or zizgzag patterns. The prints, embedded in fossilised volcanic ash, are about 20 cm (eight inches) long and 10 cm wide and belonged to primitive humans who were about 1.5 metres tall.

Oldest human footprints found BBC
Oldest human footprints found on volcano New Scientist
Earliest human footprints found? Nature
  ¶ 4:12 pm