Millimeter-size spherules from an ancient impact. 
Photo credit Oberlin College/Bruce M. Simonson.

Most of Earth's oldest impact craters, even those from colossal collisions, have been lost due to weathering and tectonic forces. News releases April 25th from Purdue University and the Southwest Research Institute (SwRI) report that new tools allow these impacts to be studied through thin layers of spherules that condensed from plumes of vaporized rock thrown high above Earth, such as these examples, each about a millimeter wide, from Western Australia (Jeerinah layer) from an event with worldwide affects 2.63 billion years ago. Photo credit: Oberlin College/Bruce M. Simonson.

Contents  on 27 April '12

Asteroid/Comet Connection (A/CC) Resources:

The latest A/CC news is available via framed access, RSS news feed RSS news feed, or redirection. - Note: A/CC has a main Web site and also a backup site with its own duplicate RSS news feed.

Navigation tips: Use the << and >> arrows on the menus for each regular section (Observers, Risks, etc.) to move to the previous and next day's news for that section. Use the Index menu item to access specific days through a calendar interface. And use the all-up news archive to access news from any time since A/CC began in early 2002. To keep track of what's new each day, watch the Chronology section.

Traffic Report  on 27 April '12

Four objects reported inside ten LD

Four asteroids are reported traveling within ten lunar distances (LD) of Earth today. Inside Earth's Hill sphere, radar target 2012 HM moves from 2.50 to 1.57 LD and risk-listed 2012 HP13 comes its closest to Earth this time around, reaching 1.98 LD at 0625 UTC, as well as its closest to the Moon -- 1.10 LD at 1024 UTC.

Out further, risk-listed 2012 HG2 is outbound from 7.21 to 7.99 LD and 2012 HN1 from 8.43 to 9.40 LD.

Coming to the neighborhood next, 1992 JD arrives inside ten LD on April 30th and 2010 KK37 on May 15th.

This report was generated at 1312 UTC with follow-up in today's DOU MPEC for 2012 HP13 and 2012 HM.

Notes: Ten times the distance to the Moon (ten LD) has no astronomical significance but is a useful reporting boundary. Earth's Hill sphere (of gravitational influence) is estimated to extend out to around 3.89 LD. Object distances are interpreted by A/CC from JPL Horizons data. See also current sky chart and object details (alt-details), ephemerides, and today's timeline.

NEOCP Activity  on 27 April '12

The MPC's NEO Confirmation Page has 20 listings

When last checked at 2358 UTC today, the Minor Planet Center's Near Earth Object discovery Confirmation Page (NEOCP) had 20 objects listed. Of these, nine were "one nighters." So far The Tracking News has counted a total of 43 listings on the NEOCP today.

To learn how observers use the NEOCP, see the Practical guide on how to observe NEOCP object at Suno Observatory by Birtwhistle et al.

New MPECs  on 27 April '12

Minor Planet Electronic Circulars

As of last check at 2359 UTC, there has been one MPEC posted today from the International Astronomical Union's Minor Planet Center in Cambridge, Massachusetts.

<< DOU on 27 Apr. '12 >>  MPEC 2012-H75 - "06:03 UT" - Daily Orbit Update

Observers  on 27 April '12

Sixteen observers appear in today's MPEC.

CodeObserver / observatory
I27Barred Owl Obs., 2 in MPEC 2012-H75 -- 2012 HP13, 2012 HM
300Bisei Spaceguard Center in Japan, 1 in MPEC 2012-H75 -- 2012 HC20
160Castelmartini Obs. in Italy, 5 in MPEC 2012-H75 -- 2012 HP13, 2012 HM, 2012 HL, 2012 DO, 2001 SZ269
F65%Tim Lister in southern California via Faulkes Telescope North in Hawaii, 2 in MPEC 2012-H75 -- 2012 HP13, 2012 HM
C73Galati Obs. in Romania, 4 in MPEC 2012-H75 -- 2010 KX7, 86667, 312473, 24475
695]Mark Trueblood via Kitt Peak Natl. Obs. (KPNO) in Arizona, 2 in MPEC 2012-H75 -- 2012 HM, 2012 HG8
C01Lohrmann Obs. in Germany, 4 in MPEC 2012-H75 -- 96590, 284114, 1865, 1620
C41MASTER-II Obs. Kislovodsk in Russia, 1 in MPEC 2012-H75 -- 263976
5682David Tholen's team on Mauna Kea in Hawaii, 2 in MPEC 2012-H75 -- 2012 HP13, 2012 GV17
A13Naef Obs. in Switzerland, 2 in MPEC 2012-H75 -- 2012 HM8, 141531
F51Pan-STARRS 1 (PS1) in Hawaii, 17 in MPEC 2012-H75 -- 2012 HY1, 2012 HM1, 2012 GX11, 2012 DO, 2010 LJ14, 2010 CG18, 2003 SV222, 2003 SL5, 86667, 66407, 189008, 186822, 152889, 144861, 136874, 10150, 7341
H23Pear Tree Obs. in Florida, 1 in MPEC 2012-H75 -- 2012 HP13
104San Marcello Pistoiese Obs. in Italy, 1 in MPEC 2012-H75 -- 2012 HP13
H36Sandlot Obs. in Kansas, 1 in MPEC 2012-H75 -- 2009 XG8
J84South Obs. in England, 1 in MPEC 2012-H75 -- 2012 HP13
291Spacewatch 1.8m telescope in Arizona, 1 in MPEC 2012-H75 -- 2012 HO13
For a list of all participating observatories that have Web addresses, see A/CC's Observatory Links page.

Impact Risk Monitoring  on 27 April '12

Summary Risk Table for Risk Assessments Updated Today   (last checks: NEODyS and JPL at 2359 UTC)
See the CRT page for a list of all objects rated recently as risks and our ephemerides page for a list of risk-listed objects under current observation.
The time horizon for JPL is 100 years from today and for NEODyS is usually the year 2090. Both also post impact solutions beyond 100 years for a few special objects.
For the latest official risk assessments, and for explanations of the terminology, see the JPL NEO Program Sentry and NEODyS CLOMON2 risk pages.





Notes for Today's Latest Risk Assessments
2012 HP13JPL Sentry22592077-2100104.8e-07-6.06-6.640JPL: "Analysis based on 150 observations spanning 4.4542 days (2012-Apr-22.46032 to 2012-Apr-26.91457)." Diameter approximately 0.050 km. from mean, weighted H=24.2.
NEODyS13082069-2088143.79e-07-6.12-6.750NEODyS: "Based on 156 optical observations (of which 9 are rejected as outliers) from 2012-04-22.461 to 2012-04-26.915."
2012 HM8JPL Sentry1308R E M O V E DJPL: Risk listing removed at 0850 UTC.
2012 HG8JPL Sentry1308203011.7e-06-2.50-2.500JPL: "Analysis based on 133 observations spanning 6.9249 days (2012-Apr-20.25484 to 2012-Apr-27.17974)." Diameter approximately 0.370 km. from mean, weighted H=19.8.
NEODyS13082030-203016.48e-07-2.93-2.930NEODyS: "Based on 134 optical observations (of which 1 are rejected as outliers) from 2012-04-20.256 to 2012-04-27.181."
2012 GV17NEODyS13082035-2090301.51e-07-4.92-5.210NEODyS: "Based on 28 optical observations (of which 0 are rejected as outliers) from 2012-04-14.343 to 2012-04-25.499."

Legend: VI# = VI count, Prob Cum = cumulative probability, PS Cum/Max = cumulative/maximum Palermo Scale, TS = Torino Scale

An impact solution, also known as a "virtual impactor" (VI), is not a prediction but rather a possibility derived from a variant orbit calculation that cannot be eliminated yet based on the existing data. Elimination can come quickly with just a little further observation or may take weeks or months, sometimes years. Once superceded or eliminated, a former impact solution has zero relevance to an object's risk. See Jon Giorgini's "Understanding Risk Pages" to learn more.

Chronology  on 27 April '12

Times are UTC for when items were noted or added by The Tracking News.

2259Noted that JPL Sentry has updated its 2012 HP13 risk assessment - see above
1312Generated Traffic Report
1308Noted that NEODyS has updated its 2012 GV17 risk assessment - see above
Noted that JPL Sentry has updated its 2012 HG8 risk assessment - see above
Noted that NEODyS has updated its 2012 HG8 risk assessment - see above
Noted that JPL Sentry has removed 2012 HM8 as an impact risk - see above
Noted that NEODyS has updated its 2012 HP13 risk assessment - see above
Grabbed MPEC 2012-H75 - Daily Orbit Update - see above