Search found 3 matches
- Thu Sep 27, 2012 6:37 am
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: APOD: Unusual Spheres on Mars (2012 Sep 25)
- Replies: 45
- Views: 6668
Re: APOD: Unusual Spheres on Mars (2012 Sep 25)
From the structure an presence of cross bedding of the matrix in which the spheres are enclosed, I would guess that these are Oolites - calcium, phosphate or even haematite formed by accretion around a seed, ususually a sand grain. On earth ooids form in shallow lakes subject to current action, whic...
- Tue Sep 25, 2012 8:28 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: APOD: Unusual Spheres on Mars (2012 Sep 25)
- Replies: 45
- Views: 6668
Re: APOD: Unusual Spheres on Mars (2012 Sep 25)
Based on their form and apearance, plus the obvious current bedding between the spheres, I would say that they are most propably Oolites. Ooids can be composed of Calcium (Aragonite), phosphate, or Haematite. Their formation is caused by chemical precipitation and accretion around a seed particle, o...
- Wed Aug 15, 2012 12:07 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: APOD: Layered Hills in Arabia Terra on Mars (2010 Aug 15)
- Replies: 31
- Views: 6265
Re: APOD: Layered Hills in Arabia Terra on Mars (2010 Aug 15
As a geologist, I find this image very intriguing. Flat lying strata comprising the Mesas shows no evidence of deformation, indicating that the deposits that formed the Mesas were laid down during a period of no tectonic activity (at least in the Arabia Terra region), with folding and faulting absen...