Source: IAU Newsletter
The MESSENGER Education and Public Outreach (EPO) Team is launching a competition this week to name five impact craters on Mercury in conjunction with the IAU. (learn more)
ESA's Venus Express has ended its eight-year mission after far exceeding its planned life. The spacecraft exhausted its propellant during a series of thruster burns to raise its orbit following the low-altitude aerobraking earlier this year.
Since its arrival at Venus in 2006, Venus Express had been on an elliptical 24 hour orbit, travelling 66 000 km above the south pole at its furthest point and to within 200 km over the north pole on its closest approach, conducting a detailed study of the planet and its atmosphere.
However, after eight years in orbit and with propellant for its propulsion system running low, Venus Express was tasked in mid-2014 with a daring aerobraking campaign, during which it dipped progressively lower into the atmosphere on its closest approaches to the planet.
Normally, the spacecraft would perform routine thruster burns to ensure that it did not come too close to Venus and risk being lost in the atmosphere. But this unique adventure was aimed at achieving the opposite, namely reducing the altitude and allowing an exploration of previously uncharted regions of the atmosphere.
The campaign also provided important experience for future missions - aerobraking can be used to enter orbit around planets with atmospheres without having to carry quite so much propellant.
Between May and June 2014, the lowest point of the orbit was gradually reduced to about 130-135 km, with the core part of the aerobraking campaign lasting from 18 June to 11 July.
After this month of 'surfing' in and out of the atmosphere at low altitudes, the lowest point of the orbit was raised again through a series of 15 small thruster burns, such that by 26 July it was back up to about 460 km, yielding an orbital period of just over 22 hours.
The mission then continued in a reduced science phase, as the closest approach of the spacecraft to Venus steadily decreased again naturally under gravity.
Under the assumption that there was some propellant still remaining, a decision was taken to correct this natural decay with a new series of raising manoeuvres during 23-30 November, in an attempt to prolong the mission into 2015.
However, full contact with Venus Express was lost on 28 November. Since then the telemetry and telecommand links had been partially re-established, but they were very unstable and only limited information could be retrieved.
"The available information provides evidence of the spacecraft losing attitude control most likely due to thrust problems during the raising manoeuvres," says Patrick Martin, ESA's Venus Express mission manager.
"It seems likely, therefore, that Venus Express exhausted its remaining propellant about half way through the planned manoeuvres last month."
Unlike cars and aircraft, spacecraft are not equipped with fuel gauges, so the time of propellant exhaustion for any satellite - especially after such a long time in space - is difficult to predict. The end could not be predicted but was not completely unexpected either.
Without propellant, however, it is no longer possible to control the attitude and orient Venus Express towards Earth to maintain communications. It is also impossible to raise the altitude further, meaning that the spacecraft will naturally sink deeper into the atmosphere over the coming weeks.
"After over eight years in orbit around Venus, we knew that our spacecraft was running on fumes," says Adam Williams, ESA's acting Venus Express spacecraft operations manager.
"It was to be expected that the remaining propellant would be exhausted during this period, but we are pleased to have been pushing the boundaries right down to the last drop."
"During its mission at Venus, the spacecraft provided a comprehensive study of the planet's ionosphere and atmosphere, and has enabled us to draw important conclusions about its surface," says Håkan Svedhem, ESA's Venus Express project scientist.
Venus has a surface temperature of over 450°C, far hotter than a normal kitchen oven, and its atmosphere is an extremely dense, choking mixture of noxious gases.
One highlight from the mission is the tantalising hint that the planet may well be still geologically active today. One study found numerous lava flows that must have been created no more than 2.5 million years ago - just yesterday on geological timescales - and possibly even much less than that.
Indeed, measurements of sulphur dioxide in the upper atmosphere have shown large variations over the course of the mission. Although peculiarities in the atmospheric circulation may produce a similar result, it is the most convincing argument to date of active volcanism.
Even though the conditions on the surface of Venus are extremely inhospitable today, a survey of the amount of hydrogen and deuterium in the atmosphere suggests that Venus once had a lot of water in the atmosphere, which is now mostly gone, and possibly even oceans of water like Earth's.
Also just like Earth, the planet continues losing parts of its upper atmosphere to space: Venus Express measured twice as many hydrogen atoms escaping out of the atmosphere as oxygen atoms. Because water is made of two hydrogen atoms and one oxygen atom, the observed escape indicates that water is being broken up in the atmosphere.
Studies of the planet's 'super-rotating' atmosphere - it whips around the planet in only four Earth-days, much faster than the 243 days the planet takes to complete one rotation about its axis - also turned up some intriguing surprises. When studying the winds, by tracking clouds in images, average wind speeds were found to have increased from roughly 300 km/h to 400 km/h over a period of six Earth years.
At the same time, a separate study found that the rotation of the planet had slowed by 6.5 minutes since NASA's Magellan measured it before completing its five-year mission at Venus 20 years ago. However, it remains unknown if there is a direct relationship between the increasing wind speeds and the slowing rotation.
"While the science collection phase of the mission is now complete, the data will keep the scientific community busy for many years to come," adds Håkan.
"Venus Express has been part of our family of spacecraft in orbit since it was launched in 2005," says Paolo Ferri, Head of ESA Mission Operations.
"It has been an exciting experience to operate this marvellous spacecraft in the Venus environment. The scientific success of the mission is a great reward for the work done by the operations teams and makes us more proud than sad in this moment of farewell."
"While we are sad that this mission is ended, we are nevertheless happy to reflect on the great success of Venus Express as part of ESA's planetary science programme and are confident that its data will remain important legacy for quite some time to come," says Martin Kessler, Head of ESA Science Operations.
"The mission has continued for much longer than its planned lifetime and it will now soon go out in a blaze of glory."
"Venus Express was an important element of the scientific programme of ESA and, even though mission operations are ending, the planetary science community worldwide will continue to benefit from more than eight years of Venus Express data and major discoveries which foster the knowledge of terrestrial planets and their evolution," says Alvaro Giménez, ESA's Director of Science and Robotic Exploration.
Source: NASA Science News
A popular theory holds that ocean water was brought to Earth by the ancient impacts of comets and asteroids. However, new data from the European Space Agency’s Rosetta spacecraft indicate that terrestrial water did not come from comets like 67P/Churyumov-Gerasimenko.(learn more)
The goal of the European Astronomy Contest Catch a Star is to stimulate the creativity and independent work of students, to strengthen and expand their astronomical knowledge and skills, and to help the spread of information technologies in the educational process.
For more information about the contest please visit the official site at http://www.eaae-astronomy.org/catchastar/
The EAAE has associated to the Physics Department José Juan Gambiagi, of Buenos Aires, IAU, the Asociación Física Argentina and the Projeto Eratostenes Brasil to perform a worldwide Eratostenes Experiment using data from schools all around the world.
To allow the simultaneous participation of schools from northern and southern hemispheres that have different school calendars, the experiment shall be reproduced on the autumn equinox that will occur on September 21st , 2014.
On a window of dates between September 18th and September 24th, 2014 the schools must measure the shadow of the Sun as it passes the local meridian, as explained on the links of the Main Menu on the left side of this page.
EAAE has performed this Experiment in the past with students all around Europe in 1997 and in 2010, and this year's event marks the beginning of the annual basis of the project in EAAE's strategy. The Physics Department José Juan Gambiagi, of Buenos Aires, that has been performing this experiment in South America in the last years (learn more at http://df.uba.ar/eratostenes) and will be responsible for the database of all measurements.
To make your registration plese visit http://www.eaae-astronomy.org/eratosthenes/
The European Southern Observatory (ESO) and its Science Outreach Network are collaborating with the science communication event organiser Sterrenlab to arrange the second ESO Astronomy Camp — Measuring the Universe. The camp will take place from 26 December 2014 to 1 January 2015 at the Astronomical Observatory of the Autonomous Region of the Aosta Valley, located in Saint-Barthelemy, Nus, Italy. Several partners, including ESO, are providing bursaries that will be awarded to the winning applicants.
The camp will explore the theme of distances in astronomy through lectures, hands-on activities, and nighttime observations with the telescopes and instruments at the observatory. Social activities, winter sports, and excursions will contribute to making the camp a memorable experience for the participants. ESO will be responsible for the scientific programme for the ESO Astronomy Camp, and will provide lecturers and material together with several other partners.
A registration fee of 500 euros covers full board accommodation at the hostel in Saint Barthelemy, supervision by professional staff, all astronomical and leisure activities, materials, excursions, internal transport, and insurance. Bus transport between the observatory and the airport of Milan Malpensa will be provided. The fee does not include travel costs between the student’s home and Milan Malpensa or Saint Barthelemy.
The camp will accommodate a maximum of 56 secondary school students aged between 16 and 18 (born in the years 1996/7/8) from the ESO Member States and ESO Science Outreach Network countries. A limited number of places will be available to students from other countries, but they will not be eligible to receive the ESO bursaries.
Students wishing to apply should fill out the form on the Camp website before 20 October 2014. Eligible students who wish to apply for a bursary should in addition send a one-page text or a video explaining why they deserve to win. The selection of the candidates will take place on 31 October 2014. Final confirmation from the participants that they will attend will be due by 10 November 2014. The selection criteria and other instructions for participation are given on the Camp website.
EAAE: Cristina Palici di Suni (firstname.lastname@example.org)
More information HERE (at ESO website).
Source: NASA Science News
OSIRIS narrow angle camera view of 67P/C-G from a distance of 1000 km on 1 August 2014.
Note that the dark spot is an artefact from the onboard CCD camera associated to bad pixels.
Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
As the European Space Agency's Rosetta spacecraft closes to within 1000 km of Comet 67P/Churyumov-Gerasimenko, the Rosetta science team has released a new image and temperature measurements of the comet's core. The temperature data show that 67P is too hot to be covered in ice and must instead have a dark, dusty crust.(learn more)
Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have found wildly misaligned planet-forming gas discs around the two young stars in the binary system HK Tauri. These new ALMA observations provide the clearest picture ever of protoplanetary discs in a double star. The new result also helps to explain why so many exoplanets — unlike the planets in the Solar System — came to have strange, eccentric or inclined orbits. The results were published in the journal Nature on 31 July 2014. (learn more)
Source: NASA Science News
NASA's Opportunity Mars rover, which landed on the Red Planet in 2004, now holds the off-Earth driving record of 25+ miles, and is not far from completing a full extraterrestrial marathon.(learn more)
Source: ESA/Hubble Science heic1416
Astronomers using the NASA/ESA Hubble Space Telescope have mapped the mass within a galaxy cluster more precisely than ever before. Created using observations from Hubble's Frontier Fields observing programme, the map shows the amount and distribution of mass within MCS J0416.1–2403, a massive galaxy cluster found to be 160 trillion times the mass of the Sun. The detail in this mass map was made possible thanks to the unprecedented depth of data provided by new Hubble observations, and the cosmic phenomenon known as strong gravitational lensing. (read more)
Source: ESO Photo Release eso1422
In this striking new image from ESO’s La Silla Observatory in Chile young stars huddle together against a backdrop of clouds of glowing gas and lanes of dust. The star cluster, known as NGC 3293, would have been just a cloud of gas and dust itself about ten million years ago, but as stars began to form it became the bright group of stars we see here. Clusters like this are celestial laboratories that allow astronomers to learn more about how stars evolve. (learn more)
Astronomers using the NASA/ESA Hubble Space Telescope have probed the extreme outskirts of the stunning elliptical galaxy Centaurus A. The galaxy’s halo of stars has been found to extend much further from the galaxy’s centre than expected and the stars within this halo seem to be surprisingly rich in heavy elements. This is the most remote portion of an elliptical galaxy ever to have been explored.(learn more)
Credit: NASA Science News
New images of Comet 67P/Churyumov-Gerasimenko show that the target of ESA's Rosetta probe is no ordinary comet.
Comet 67P/Churyumov-Gerasimenko, was imaged on 14 July 2014 by OSIRIS, Rosetta's scientific imaging system, from a distance of approximately 12 000 km (image on the right).
The image suggests that the comet may consist of two parts: one segment seems to be rather elongated, while the other appears more bulbous.(learn more)