The Basilica of Santa Sabina in Rome -- this is the station Church for Ash Wednesday, where the Supreme Roman Pontiff traditionally presides over the Ash Wednesday Mass.
On this day we open the great penitential season of Lent. Memento, homo, quia pulvis es, et in pulverem reverteris. Remember man that thou art dust, and unto dust thou shalt return! (Gen 3:19)
Ashes have, from time immemorial symbolized "grief, mourning, or repentance." How fitting that, on this day, we put on ashes to outwardly manifest our interior repentance -- ashes made from burning the blessed palms of the previous Holy Week.
The liturgies and prayers of this day are sublime:
"Almighty and everlasting God, spare the penitent...bless these ashes, that they may be a remedy to all who invoke Thy Name...O God, who desirest not the death but the conversion of sinners, look in kindness upon our human frailty...and bless those ashes, so that we, who know ourselves to be but ashes...and the we must return to dust, may deserve to obtain pardon and the rewards offered to the penitent."
My favorite, after the imposition of the ashes is this prayer:
"Grant us, Lord, the grace to begin the Christian's war of defense with holy fasts; that, as we do battle with the spirits of evil, we may be protected by the help of self-denial."
Today we begin the Lenten season in preparation for Easter. Traditionally, in the Latin Church, today marks a period of forty days of fasting (Sundays excluded). While the minimum may be lowered to merely Ash Wednesday and Good Friday, surely our appreciation for the value of fasting and penance, and reverence for tradition, spurs us on to mortify our appetites in this way!
For more on this splendid, if somber, Feast, you might note:
Old Catholic Encyclopedia: Ash Wednesday
Customs of Ash Wednesday (Fisheaters)
Catholic Culture: Ash Wednesday
Old Catholic Encyclopedia: Lent
Customs of Lent (Fisheaters)
Catholic Culture: Lent
Here is a link that goes into more detail about the ashes of this day:
Catholic Culture: Why Ashes?
The Code of Canon Law, 1983, lays down for us several points about this penitential season (emphasis mine):
"Can. 1249 The divine law binds all the Christian faithful to do penance each in his or her own way. In order for all to be united among themselves by some common observance of penance, however, penitential days are prescribed on which the Christian faithful devote themselves in a special way to prayer, perform works of piety and charity, and deny themselves by fulfilling their own obligations more faithfully and especially by observing fast and abstinence, according to the norm of the following canons.
Can. 1250 The penitential days and times in the universal Church are every Friday of the whole year and the season of Lent.
Can. 1251 Abstinence from meat, or from some other food as determined by the Episcopal Conference, is to be observed on all Fridays, unless a solemnity should fall on a Friday. Abstinence and fasting are to be observed on Ash Wednesday and Good Friday.
Can. 1252 The law of abstinence binds those who have completed their fourteenth year. The law of fasting binds those who have attained their majority, until the beginning of their sixtieth year. Pastors of souls and parents are to ensure that even those who by reason of their age are not bound by the law of fasting and abstinence, are taught the true meaning of penance.
Can. 1253 The conference of bishops can determine more precisely the observance of fast and abstinence as well as substitute other forms of penance, especially works of charity and exercises of piety, in whole or in part, for abstinence and fast."
(cf., Code of Canon Law)
Finally, here is a link with a little information about today's station Church in Rome -- Santa Sabina on the Aventine Hill, a Dominican Basilica: Roman Church Wiki: Santa Sabina
Here is a splendid explanation of the role of Santa Sabina by the Dominicans themselves: Order of Preachers: Why does Lent start on the Aventine Hill?
Finally, a splendid motet by the Englishman William Byrd, setting to music one of the liturgical texts of Ash Wednesday:
Here is the text, with a translation:
Emendemus in melius quae ignoranter peccavimus;
ne subito praeoccupati die mortis,
quaeramus spatium poenitentiae,
et invenire non possimus.
Attende, Domine, et miserere;
quia peccavimus tibi.
Deus salutaris noster,
et propter honorem nominis tui libera nos.
Let us amend for the better in those things in which we have sinned through ignorance;
lest suddenly overtaken by the day of death,
we seek space for repentance,
and be not able to find it.
Hearken, O Lord, and have mercy:
for we have sinned against thee.
Help us, O God of our salvation,
and for the honour of thy name deliver us.
(English translation by William Mahrt)
(Ps. 78:9; Distribution of Ashes, Ash Wednesday; First Sunday of Lent, Matins Responsory; cf. Esther 13, Joel 2)