Video: Departing Earth from Messenger

The Mercury-bound MESSENGER spacecraft captured several stunning images of Earth during a gravity assist swingby of its home planet on Aug. 2, 2005. Several hundred images, taken with the wide-angle camera in MESSENGER’s Mercury Dual Imaging System (MDIS), were sequenced into a movie documenting the view from MESSENGER as it departed Earth.

Comprising 358 frames taken over 24 hours, the movie follows Earth through one complete rotation. The spacecraft was 40,761 miles (65,598 kilometers) above South America when the camera started rolling on Aug. 2. It was 270,847 miles (435,885 kilometers) away from Earth – farther than the Moon’s orbit – when it snapped the last image on Aug. 3.

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

The Earth’s center is 1,000 degrees hotter than previously thought

This artist's view depicts the different layers of the Earth and their representative temperatures: crust, upper and lower mantle (brown to red), liquid outer core (orange) and solid inner core (yellow). The pressure at the border between the liquid and the solid core (highlighted) is 3.3 million atmospheres, with a temperature now confirmed as 6000 degrees Celsius. Credit: ESRF

This artist’s view depicts the different layers of the Earth and their representative temperatures: crust, upper and lower mantle (brown to red), liquid outer core (orange) and solid inner core (yellow). The pressure at the border between the liquid and the solid core (highlighted) is 3.3 million atmospheres, with a temperature now confirmed as 6000 degrees Celsius. Credit: ESRF

Scientists have determined the temperature near the Earth’s centre to be 6000 degrees Celsius, 1000 degrees hotter than in a previous experiment run 20 years ago. These measurements confirm geophysical models that the temperature difference between the solid core and the mantle above, must be at least 1500 degrees to explain why the Earth has a magnetic field. The scientists were even able to establish why the earlier experiment had produced a lower temperature figure. The results are published on 26 April 2013 in Science….
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Earth’s magnetic shield behaves like a sieve

When the Earth’s magnetic field and the interplanetary magnetic field are aligned, for example in a northward orientation as indicated by the white arrow in this figure, Kelvin–Helmholtz waves are generated at low (equatorial) latitudes. (Courtesy: ESA/AOES Medialab)

The Earth’s magnetic field is more permeable than previously thought, according to researchers analysing data from the European Space Agency’s Cluster mission. The findings have implications for modelling the dangers posed by space weather and could also help us better understand the magnetic environments around Jupiter and Saturn.
The Cluster mission, launched in 2000, comprises four identical satellites flying in a tetrahedral formation in close proximity to Earth. With highly elliptical orbits, the satellites are able to sweep in and out of the Earth’s magnetic environment, building up a 3D picture of interactions between the solar wind and our planet. The solar wind is a stream of charged particles from the outer layers of the Sun blowing into the solar system. The Earth’s magnetic field is thought to form a protective barrier against it.
It is well known, however, that if the magnetic field of the incoming solar wind has the opposite orientation to the Earth’s magnetic field, then the field lines can break and join up again in a process known as “magnetic reconnection”. This process allows the plasma from the solar wind to breach the boundary of the Earth’s magnetic field – the magnetopause – where it can then potentially reach our planet…..
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Best of “Earth As Art” – Top Five

Landsat has been collecting data of the Earth’s surface since 1972. Some of the images are visually striking, and they have been selected for the “Earth As Art” collection. These are the best.
A series of Landsat satellites have surveyed the Earth’s surface since 1972. In that time, Landsat data have become a vital reference worldwide, used for understanding scientific issues related to land use and natural resources. However, some Landsat images are simply striking to look at – presenting spectacular views of mountains and valleys, forests and farms. To celebrate the 40th anniversary of Landsat, the US Geological Survey and NASA asked for your help in selecting the top five Earth As Art images.

Dynamic Earth

Watch as this NASA animation shows the sun blasting out a giant explosion of magnetic energy called a coronal mass ejection and the Earth being shielded from this by its powerful magnetic field. The sun also continuously showers the Earth with light and radiation energy. Much of this solar energy is deflected by the Earth’s atmosphere or reflected back into space by clouds, ice and snow. What gets through becomes the energy that drives the Earth system, powering a remarkable planetary engine — the climate.

The unevenness of this solar heating, the cycles of day and night, and our seasons are part of what cause wind currents to circulate around the word. These winds drive surface ocean currents and in this animation you can view these currents flowing off the coast of Florida.

This animation connects for the first time a series of computer models. The view of the sun and the Earth’s magnetic field comes from the Luhmann-Friesen magnetic field model and two models that incorporated data from a real coronal mass ejection from the sun on December 2006.

NASA’s Community Coordinated Modeling Center (CCMC) at Goddard Space Flight Center, a multi-agency partnership that provides information on space weather to the international research community, generated these two models. The ENLIL model is a time-dependent 3-D magnetohydrodynamic model of the heliosphere and shows changes in the particles flows and magnetic fields.
The BATS-R-US model is also a magnetohydrodynamic model of plasma from solar wind moving through the Earth’s magnetic dipole field. It uses measurements of solar wind density, velocity, temperature and magnetic field by NASA’s Advanced Composition Explorer (ACE) satellite, which launched in August of 1997 and the Solar Terrestrial Relations Observatory (STEREO), two satellites that view the structure and evolution of solar storms.

The view of the Earth’s atmosphere comes from the Modern-Era Retrospective Analysis for Research and Applications (MERRA), a computer model that uses data from the Goddard Earth Observing System Data Assimilation System Version 5 (GEOS-5) and incorporates information gathered from ground stations, operational satellites and NASA’s Earth-observing fleet of satellites. The model for the ocean is the Estimating the Circulation and Climate of the Ocean, Phase II (ECCO2), a joint project of the Massachusetts Institute of Technology in Cambridge, Mass. and NASA’s Jet Propulsion Laboratory in Pasadena, Ca.

Super-Powerful X-Ray Beam Will Probe the Center of the Earth

Beamline Sample This image shows the heating of a catalyst sample in an "in situ" cell at actual operating conditions. The catalyst is studied using time-resolved X-ray absorption spectroscopy. A new beamline at the European Synchrotron Radiation Facility has a resolution of a few microseconds. ESRF

It is much easier to get to Mars than to get deep inside this planet, so for all our knowledge about things like earthquakes and the magnetic field, Earth’s interior is actually very poorly understood. To study how metals interact at the prodigious pressures within, scientists squeeze small particles in the lab and heat them up — but this is an inexact science and difficult to do. A newly revamped X-ray beam facility in Europe may be able to improve matters, and shed some light on just what is going on at the center of our planet.
The European Synchrotron Radiation Facility inaugurates its new ID24 beam today, in preparation for experiments next spring. It will enable scientists to exact extreme pressures and temperatures on metals, aiming to understand how they act at Earth’s core. It will also be able to study new chemical catalysts and battery technology, among other atomic reactions.
A synchrotron is a type of particle accelerator — the Tevatron is one — that can be used for a wide range of applications. One such application involves harnessing the accelerated particles’ electromagnetic radiation for scientific imaging. Synchrotron light sources use a series of magnetic fields to bend this radiation into different wavelengths of light. At ESRF, beamlines branch off from the particle acceleration ring to capture the particles’ (usually electrons) radiation. The new beamline, ID24, will enable incredibly fast X-ray absorption spectroscopy.
This works by firing an intense X-ray beam at a sample, and watching how atoms of the different elements inside the sample absorb the X-rays — it’s an active probe, monitoring its own experiments. The beamline has an array of germanium detectors that can take 1 million measurements per second, according to an ESRF news release. So scientists could take a small sample of iron, put it in the beamline, heat it to 10,000 degrees, and watch what happens. This would conceivably help scientists understand how iron behaves 1,500 miles beneath the surface of the Earth, and what are the melting points of other metals present in the mantle and core. This, in turn, could shed some light on things like Earth’s dynamo, which creates its magnetic field.
The ID24 beam is the first of eight new beamlines at ESRF, part of a $245 million (180 million Euro) upgrade.

Laser gyroscope measures the Earth’s ‘wobble’

Image of the Earth with the rotational axis and the magnetic field lines

An international team of researchers have developed a new type of gyroscope that is the first to measure the “wobble” in the rotational axis of the Earth from a ground-based laboratory. Astronomers normally track this wobble by continuously monitoring the position of distant objects, such as quasars. But this new method will provide a much simpler and cheaper alternative to these large-scale astronomical readings, the scientists claim.

The International Association of Geodesy, which was involved in this effort, maintains the terrestrial and celestial reference frames, which form an essential basis for navigation and the study of the Earth. The terrestrial reference frame is relevant to an observer on the Earth’s surface. For example, it describes why the Sun appears to be rising and setting every day, when we know that it is the Earth itself that rotates. The celestial reference frame – based at the centre of the solar system – is calculated using 212 distant astronomical bodies such as quasars and is used to determine the position of all the planets including the Earth.

Distant markers

The precise knowledge of Earth’s rotation and the orientation of the rotational axis as a function of time are necessary to link the two reference frames with sufficient accuracy. For many decades now, this has been done using radio telescope observations, based on a technique known as Very Long Baseline Interferometry (VLBI). Unfortunately, this is an expensive and a highly involved approach, spanning stations across the entire Earth, and until today this system cannot be operated continuously. Without the precise knowledge of the length of day and the orientation of the Earth, it is impossible to establish local positions from the Global Navigation Satellite Systems (GNSS) accurately enough.

Wobbling world

Tracking this orientation is complicated by the fact that the Earth wobbles about its axis. Both the Chandler and the annual wobble are small irregularities in the position of the Earth’s geographic poles and hence a shift in its rotational axis. The annual wobble is due to a small change in tilt as a result of the gravitational attraction due to the slight ellipticity of the Earth’s orbit. The Chandler wobble is a 435 day oscillation of the Earth’s axis attributed to factors such as ocean floor pressure variation and wind. Since the Chandler signal is particularly unpredictable, it is necessary to measure and keep track of it.

Now, Ulrich Schreiber at the Technical University of Munich and colleagues have used ring lasers – which have been used for aircraft guidance for many years now – and increased their sensitivity and stability over several orders of magnitude in order to make them suitable for monitoring the long-period changes in the Earth’s axis such as the Chandler wobble.

The ring

A ring laser uses two single-mode laser beams that propagate around a closed laser cavity in opposing directions. If a ring laser is rotating, the two opposing waves are slightly shifted in frequency and a beat interference pattern is observed, which is proportional to the rate of rotation. Since the sensor is rigidly attached to the Earth, it becomes capable of sensing small variations in the Earth’s rotational speed and the direction of the axis of rotation. “Our G-ring is orientated horizontally. If we would place it on the equator, we would see nothing – the projection vanishes – and on the pole the signal would be maximal, but polar motion would vanish,” says Schreiber.

The team designed a vastly upscale version of an aircraft ring laser. “The commercial devices are approximately 10 cm on a side, ours is 4 m on a side,” explains Schreiber. The device is placed in a temperature stabilized vault so that signals with a frequency as low as 25 nHz can be extracted. The mirror-making technology also needed to make a large leap forward for the gyroscope to work and Schreiber explains that their ring is capable of running constantly. Their device was made out of zerodur – a ceramic glass with very low thermal expansion.

Sense and stability

Thanks to the sensitivity and stability of large ring laser gyroscope, the team were able to directly measure the combined effect of the Chandler and the annual wobble of the freely rotating Earth. Their measured data was in excellent agreement with the independent measurements by using the astronomical method.

When compared to the tried and tested VLBI method, Schreiber says that it is still early days for their method. “We are still about a factor of five short of the VLBI performance and we still would need to reduce the sensor drift further. However, when we first proposed ring lasers for this purpose in the mid-nineties, all the reviewers flagged us away – the argument being that we cannot possibly reduce the drift over several orders of magnitude and that about six orders of magnitude gain in sensitivity was unrealistic,” says an enthusiastic Schreiber, suggesting that further developments will be made in the days to come.

The research is described in Physical Review Letters.