It will be, at least, unusual to suppose that the Rigvedic form of the verse is later. The TA is a much later text. Among others the disyllabic reading of ya as iya or ia was not adopted in writing tho the parctice of disyllabic reading was never forsaken. But, if we take Panini as the authority,  this is metrical ie not grammatical.

Sorry for long lecture.

Best wishes

Dipak Bhattacharya

On Mon, Nov 9, 2015 at 5:54 AM, Harry Spier <hspier.muktabodha@gmail.com> wrote:

Adeesh Sataye wrote:

Dear Ketan,

3.062.10a    tát savitúr váreṇiyam
3.062.10b    bhárgo devásya dhīmahi
3.062.10c    dhíyo yó naḥ pracodáyāt

You can find this and other IAST version of the metrically restored RV at:
http://www.utexas.edu/cola/centers/lrc/RV/

This is the form of the original Gayatri mantra from the Rg Veda but later gayatri mantras follow a different form.

. . . . . . . . . . .vidmahe

. . . . . . . . . .. dhimahI

tan naḥ X pracodayāt

1) Are the Gayatri mantras from the Taittirīya Āraṇyaka book 10 (Mahānārāyaṇa Upaniṣad) the earliest Gayatri mantras in this later form.?

Given the sacredness afforded to the Gayatri mantra from the Rg Veda, does any of the Sanskrit literature say anything about why the later Gayatri mantras follow this different form?

Thanks,

Harry Spier

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