443 Eros: Problems with the meteorite magnetism record in attempting an asteroid match

Abstract— The magnetometer experiment (MAG) onboard the Near‐Earth Asteroid Rendezvous (NEAR)‐Shoemaker spacecraft detected no global scale magnetization and established a maximum magnetization of 2.1 times 10^?6 Am² kg^?1 for asteroid 433 Eros. This is in sharp contrast with the estimated magnetization of other S‐class asteroids (Gaspra, ?2.4 times 10^?2 Am² kg^?1; Braille, ?2.8 times 10^?2 Am² kg^?1) and is below published values for all types of ordinary chondrites. This includes the L/LL types considered to most closely match 433 Eros based on preliminary interpretations of NEAR remote geochemical experiments. The ordinary chondrite meteorite magnetization intensity data was reviewed in order to assess the reasonableness of an asteroid‐meteorite match based on magnetic property measurements. Natural remanent magnetization (NRM) intensities for the ordinary chondrite meteorites show at least a 2 order of magnitude range within each of the H, L, and LL groups, all well above the 2.1 times 10^?6 Am² kg^?1 level for 433 Eros. The REM values (ratio of the NRM to the SIRM (saturation remanent magnetization)) range over 3 orders of magnitude for all chondrite groups indicating no clear relationship between NRM and the amount of magnetic material. Levels of magnetic noise in chondrite meteorites can be as much as 70% or more of the NRM. Consequently, published values of the NRM should be considered suspect unless careful evaluation of the noise sources is done. NASA Goddard SFC studies of per unit mass intensities in large (>10 000 g) and small (down to <1 g) samples from the same meteorite demonstrate magnetic intensity decreases as size increases. This would appear to be explained by demagnetization due to magnetic vector randomness at unknown scale sizes in the larger samples. This would then argue for some level of demagnetization of large objects such as an asteroid. The possibility that 433 Eros is an LL chondrite cannot be discounted.     

Astronomical Site Testing in Northwest of Argentina

We present the preliminary results of the astronomical site testing, which the group IATE of the OAC is developing in northwest of Argentine in collaboration with ESO and the Department of Astronomy of Cornell University. We show the results, which we have obtained from the analysis of GOES 8 satellite images in the 10.7 μm band, which allowed us to configurate a map of clear sky regions in an area between 23° and 28° S, and 66° 30′ and 69° W. We also comment logistical and tectonic aspects, and discuss next steps to follow in the research.     

Possibilities of GPS kinematic measurements for geological survey in East Slovakia

This paper deals with transformation procedures for observed GPS data from the world geodetic system WGS-84 into the national geodetic grid datum S-UTCN (system of united trigonometric cadaster network) and Baa (the Baltic Sea after adjustment). Transformation from WGS-84 into SUTCN is performed most frequently by means of the 7-element Helmert transformation with three identical points. Geodetic network was adjusted by two ways.     

Meridional Motions of Stable Recurrent Sunspot Groups

Stable recurrent sunspot groups from the Greenwich data set which were identified in at least two subsequent solar rotations were traced and meridional motions were determined from the two central meridian passages. In total, 327 meridional velocities were calculated and the results for the northern and the southern solar hemisphere were compared. A dependence of the solar meridional velocity vectors on the development status, latitude and position respectively to the activity belt of sunspots is investigated. The results indicate that sunspot groups are moving on the average away from the center of activity. This was found for sunspot groups growing and decreasing in area.     

EURD observations of interstellar radiation

The hot interstellar medium (ISM) has far-reaching effect upon thestructure of galaxies. Although ISM heating processes are fairly wellunderstood, after decades of study, the processes that cool the hotinterstellar medium remain obscure. The EURD spectrograph was designed tomeasure the diffuse cosmic background from 350 to 1100 Å in order tostudy the hot ISM and the mechanisms by which it sheds its energy. Wepresent the first analysis of EURD observations of the cosmic background.These EURD observations have proven to be far more sensitive than previouswork; compared to previous results, we have improved the limits to theintensity of 450 to 900 Å line emission from the ISM by one to twoorders of magnitude. Our limit to OVI 1032 Å / 1038 Å doublet of 7900ph s^-1 cm^-2 str^-1 is the lowest yet reported. The EURDlimits to line emission are less intense than predicted by a varietytheoretical models of the local ISM.     

Search for Phobos and Deimos gas/dust tori using in situ observations from Mars Global Surveyor MAG/ER

More than 490 elliptical aerobraking and science phasing orbits made by Mars Global Surveyor (MGS) in 1997 and 1998 provide unprecedented coverage of the solar wind in the vicinity of the orbits of the martian moons Phobos and Deimos. We have performed a comprehensive survey of magnetic field perturbations in the solar wind to search for possible signatures of solar wind interaction with dust or gas escaping from the moons. A total of 1246 solar wind disturbance events were identified and their distribution was examined relative to Phobos, the Phobos orbit, and the Deimos orbit. We find that the spatial distribution of solar wind perturbations does not increase near or downstream of Phobos, Phobos’ orbit, or Deimos’ orbit, which would have been expected if there is significant outgassing or dust escape from the martian moons. Of the 1246 magnetic field perturbation events found in the MGS data set, 11 events were found within 2000 km of the Phobos orbit, while three events were found within 2000 km of the Deimos orbit. These events were analyzed in detail and found to likely have other causes than outgassing/dust escape from the martian moons. Thus we conclude that the amount of gas/dust escaping the martian moons is not significant enough to induce detectable magnetic field perturbations in the solar wind. In essence we have not found any clear evidence in the MGS magnetic field data for outgassing or dust escape from the martian moons.     

The 2dF Galaxy Redshift Survey: luminosity dependence of galaxy clustering

We investigate the dependence of the strength of galaxy clustering on intrinsic luminosity using the Anglo-Australian two degree field galaxy redshift survey (2dFGRS). The 2dFGRS is over an order of magnitude larger than previous redshift surveys used to address this issue. We measure the projected two-point correlation function of galaxies in a series of volume-limited samples. The projected correlation function is free from any distortion of the clustering pattern induced by peculiar motions and is well described by a power law in pair separation over the range     . The clustering of     galaxies in real space is well-fitted by a correlation length     and power-law slope     . The clustering amplitude increases slowly with absolute magnitude for galaxies fainter than M *, but rises more strongly at higher luminosities. At low luminosities, our results agree with measurements from the Southern Sky Redshift Survey 2 by Benoist et al. However, we find a weaker dependence of clustering strength on luminosity at the highest luminosities. The correlation function amplitude increases by a factor of 4.0 between     and −22.5, and the most luminous galaxies are 3.0 times more strongly clustered than L * galaxies. The power-law slope of the correlation function shows remarkably little variation for samples spanning a factor of 20 in luminosity. Our measurements are in very good agreement with the predictions of the hierarchical galaxy formation models of Benson et al.